Narrowband time-division duplex frame structure for narrowband communications

ABSTRACT

In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may determine a narrowband TDD frame structure of a group of narrowband TDD frame structures for narrowband communications. The apparatus may transmit a series of repetitions of a narrowband physical downlink channel using the narrowband TDD frame structure. In one aspect, a first portion of repetitions from the series of repetitions may be transmitted in one or more first sets of downlink subframes using a first scrambling sequence. In one aspect, a second portion of repetitions from the series of repetitions may be transmitted in one or more second sets of downlink subframes using a second scrambling sequence.

CROSS-REFERENCE TO RELATED APPLICATION

This present application for patent is a Continuation application ofU.S. patent application Ser. No. 15/724,127 entitled “NARROWBANDTIME-DIVISION DUPLEX FRAME STRUCTURE FOR NARROWBAND COMMUNICATIONS”filed Oct. 3, 2017 which claims the benefit of Indian Application SerialNo. 201741005360, entitled “NARROWBAND TIME-DIVISION DUPLEX FRAMESTRUCTURE FOR NARROWBAND COMMUNICATIONS” and filed on Feb. 15, 2017,which is expressly incorporated by reference herein in its entirety.

BACKGROUND Field

The present disclosure relates generally to communication systems, andmore particularly, to a narrowband time-division duplex (TDD) framestructure for narrowband communications.

Background

Wireless communication systems are widely deployed to provide varioustelecommunication services such as telephony, video, data, messaging,and broadcasts. Typical wireless communication systems may employmultiple-access technologies capable of supporting communication withmultiple users by sharing available system resources. Examples of suchmultiple-access technologies include code division multiple access(CDMA) systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, orthogonal frequency divisionmultiple access (OFDMA) systems, single-carrier frequency divisionmultiple access (SC-FDMA) systems, and time division synchronous codedivision multiple access (TD-SCDMA) systems.

These multiple access technologies have been adopted in varioustelecommunication standards to provide a common protocol that enablesdifferent wireless devices to communicate on a municipal, national,regional, and even global level. An example telecommunication standardis 5G New Radio (NR). 5G NR is part of a continuous mobile broadbandevolution promulgated by Third Generation Partnership Project (3GPP) tomeet new requirements associated with latency, reliability, security,scalability (e.g., with Internet of Things (IoT)), and otherrequirements. Some aspects of 5G NR may be based on the 4G Long TermEvolution (LTE) standard. There exists a need for further improvementsin 5G NR technology. These improvements may also be applicable to othermulti-access technologies and the telecommunication standards thatemploy these technologies.

Narrowband communications involve communicating with a limited frequencybandwidth as compared to the frequency bandwidth used for LTEcommunications. One example of narrowband communication is narrowband(NB) IoT (NB-IoT) communication, which is limited to a single resourceblock (RB) of system bandwidth, e.g., 180 kHz. Another example ofnarrowband communication is enhanced machine-type communication (eMTC),which is limited to six RBs of system bandwidth, e.g., 1.08 MHz.

NB-IoT communication and eMTC may reduce device complexity, enablemulti-year battery life, and provide deeper coverage to reachchallenging locations such as deep inside buildings. Because thecoverage provided by narrowband communications may include reachingchallenging locations (e.g., a smart gas meter located in the basementof a building), there is an increased chance that one or moretransmissions will not be properly received. Hence, repeatedtransmissions may be used in narrowband communication to increase theprobability that a transmission will be properly decoded by a receiverdevice. A TDD frame structure may support repeated transmissions due toan increased number of contiguous downlink and/or uplink subframes, ascompared to a frequency division-duplex (FDD) frame structure. Thus,there is a need to support narrowband TDD frame structure for narrowbandcommunication.

SUMMARY

The following presents a simplified summary of one or more aspects inorder to provide a basic understanding of such aspects. This summary isnot an extensive overview of all contemplated aspects, and is intendedto neither identify key or critical elements of all aspects nordelineate the scope of any or all aspects. Its sole purpose is topresent some concepts of one or more aspects in a simplified form as aprelude to the more detailed description that is presented later.

Narrowband communications involve communicating with a limited frequencybandwidth as compared to the frequency bandwidth used for LTEcommunications. One example of narrowband communication is NB-IoTcommunication, which is limited to a single RB of system bandwidth,e.g., 180 kHz. Another example of narrowband communication is eMTC,which is limited to six RBs of system bandwidth, e.g., 1.08 MHz.

NB-IoT communication and eMTC may reduce device complexity, enablemulti-year battery life, and provide deeper coverage to reachchallenging locations such as deep inside buildings. However, becausethe coverage provided by narrowband communications may include reachingchallenging locations (e.g., a smart gas meter located in the basementof a building), there is an increased chance that one or moretransmissions will not be properly decoded by a receiver device.Consequently, narrowband communication may include a predeterminednumber of repeated transmissions to increase the chance of having thetransmission properly decoded by the receiver device. A TDD framestructure may be used by a narrowband communication system since certainTDD frame configurations may include a greater number of contiguousuplink and/or downlink subframes that may be used for the repeatedtransmissions, as compared to a FDD frame structure. Thus, there is aneed to support the use of narrowband TDD frame structure for narrowbandcommunication.

The present disclosure provides a mechanism to support one or morenarrowband TDD frame structure(s) for narrowband communication.

In an aspect of the disclosure, a method, a computer-readable medium,and an apparatus are provided. The apparatus may determine to transmit anarrowband physical downlink channel in a subframe in a narrowband TDDframe structure of a plurality of narrowband TDD frame structures fornarrowband communications. In addition, the apparatus may determinewhether the subframe is a special subframe or a downlink subframe whenthe narrowband TDD frame structure includes one or more specialsubframes. Further, the apparatus may determine how to transmit anarrowband physical downlink channel based on the determination whetherthe subframe is a special subframe or a downlink subframe. Additionally,the apparatus may transmit the narrowband physical downlink channel.

In another aspect, the apparatus may determine a TDD frame structure ofa group of narrowband TDD frame structures for narrowbandcommunications. In addition, the apparatus may allocate at least one RBin the narrowband TDD frame structure for transmitting a narrowbandphysical downlink channel to a first UE. Further, the apparatus may mapa UE-RS to the at least one RB allocated for transmitting the narrowbandphysical downlink channel. Additionally, the apparatus may transmit theUE-RS to the first UE based on the mapping.

In a further aspect, the apparatus may determine a narrowband TDD framestructure of a group of narrowband TDD frame structures for narrowbandcommunications. In addition, the apparatus may determine a first set ofsubframes in the narrowband TDD frame structure used for transmitting adownlink control channel to a UE. In one aspect, a last subframe in thefirst set of subframes may be subframe n. Further, the apparatus mayschedule a first uplink subframe in the narrowband TDD frame structureused by the UE for reporting a first ACK/NACK associated with thedownlink control channel. In another aspect, the first uplink subframemay be delayed based on k₀ number of subframes after the subframe n.Additionally, the apparatus may signal information associated with thek₀ number of subframes to the UE in a first delay field in a DCItransmission.

In another aspect, the apparatus may receive information indicating anarrowband TDD frame structure of a group of narrowband TDD framestructures for narrowband communications. In addition, the apparatus maymonitor one or more downlink subframes in a first radio frame thatincludes the narrowband TDD frame structure for a downlink transmissionfrom a base station. Further, the apparatus may delay at least oneuplink transmission to an uplink subframe in a second radio frame thatis subsequent to the first radio frame.

In still another aspect, the apparatus may receive informationindicating a narrowband TDD frame structure of a group of narrowband TDDframe structures for narrowband communications. Further, the apparatusmay receive a downlink grant associated with a narrowband physicaldownlink channel. The apparatus may also receive the narrowband physicaldownlink channel associated with the downlink grant over a plurality ofsubframes, the plurality of subframes including uplink subframes,downlink subframes, and special subframes. Still further, the apparatusmay receive an uplink grant associated with a narrowband physical uplinkchannel. In another aspect, the apparatus may transmit the narrowbandphysical uplink channel associated with the uplink grant using one ormore uplink subframes located at least one of before the plurality ofsubframes or after the plurality of subframes.

In still another aspect, the apparatus may receive informationindicating a narrowband TDD frame structure of a group of narrowband TDDframe structures for narrowband communications. In addition, theapparatus may receive an uplink grant associated with a narrowbandphysical uplink channel. The apparatus may also transmit the narrowbandphysical uplink channel associated with the uplink grant over aplurality of subframes. In an aspect, the plurality of subframes mayinclude uplink subframes, downlink subframes, and special subframes.Further, the apparatus may receive a downlink grant associated with anarrowband physical downlink channel. Further still, the apparatus mayreceive the narrowband physical downlink channel associated with thedownlink grant in one or more downlink subframes located at least one ofbefore the plurality of subframes or after the plurality of subframes.

In another aspect, the apparatus may determine a narrowband TDD framestructure for narrowband communications. In one aspect, the narrowbandTDD frame structure may include one or more of a set of downlinksubframes, a set of uplink subframes, a set of special subframes, or aset of flexible subframes. In addition, the apparatus may transmit abitmap associated with the narrowband TDD frame structure to a UE. In anaspect, the bitmap may include the one or more of the set of downlinksubframes, the set of uplink subframes, the set of special subframes, orthe set of flexible subframes.

In a further aspect, the apparatus may determine a narrowband TDD framestructure of a group of narrowband TDD frame structures for narrowbandcommunications. The apparatus may also transmit a series of repetitionsof a narrowband physical downlink channel using the narrowband TDD framestructure. In one aspect, a first portion of repetitions from the seriesof repetitions may be transmitted in one or more first sets of downlinksubframes using a first scrambling sequence. In another aspect, a secondportion of repetitions from the series of repetitions may be transmittedin one or more second sets of downlink subframes using a secondscrambling sequence.

In still another aspect, the apparatus may determine a narrowband TDDframe structure of a group of narrowband TDD frame structures fornarrowband communications. In addition, the apparatus may transmit afirst redundancy version of a narrowband physical downlink channel and asecond redundancy version of the narrowband physical downlink channelusing the narrowband TDD frame structure. In one aspect, a number ofrepetitions of either redundancy version may be transmitted beforeswitching between the first redundancy version and a second redundancyversion may be based on a number of downlink subframes in the determinednarrowband TDD frame structure and a predetermined maximum number ofrepetitions.

To the accomplishment of the foregoing and related ends, the one or moreaspects comprise the features hereinafter fully described andparticularly pointed out in the claims. The following description andthe annexed drawings set forth in detail certain illustrative featuresof the one or more aspects. These features are indicative, however, ofbut a few of the various ways in which the principles of various aspectsmay be employed, and this description is intended to include all suchaspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a wireless communicationssystem and an access network.

FIGS. 2A, 2B, 2C, and 2D are diagrams illustrating LTE examples of a DLframe structure, DL channels within the DL frame structure, an UL framestructure, and UL channels within the UL frame structure, respectively.

FIG. 3 is a diagram illustrating an example of an evolved Node B (eNB)and user equipment (UE) in an access network.

FIG. 4 is a diagram illustrating example narrowband TDD frame structuresin accordance with certain aspects of the disclosure.

FIG. 5 illustrates a data flow that may be used to support narrowbandcommunications using narrowband TDD frame structures in accordance withcertain aspects of the disclosure.

FIGS. 6A and 6B illustrate a data flow that may be used to supportnarrowband communications using narrowband TDD frame structures inaccordance with certain aspects of the disclosure.

FIGS. 7A and 7B illustrate a data flow that may be used to supportnarrowband communications using narrowband TDD frame structures inaccordance with certain aspects of the disclosure.

FIG. 8A illustrates a data flow that may be used to support narrowbandcommunications using narrowband TDD frame structures in accordance withcertain aspects of the disclosure.

FIG. 8B illustrates a data flow that may be used to support narrowbandcommunications using narrowband TDD frame structures in accordance withcertain aspects of the disclosure.

FIG. 8C illustrates a data flow that may be used to support narrowbandcommunications using narrowband TDD frame structures in accordance withcertain aspects of the disclosure.

FIG. 9 illustrates a data flow that may be used to support narrowbandcommunications using narrowband TDD frame structures in accordance withcertain aspects of the disclosure.

FIG. 10 illustrates a data flow that may be used to support narrowbandcommunications using narrowband TDD frame structures in accordance withcertain aspects of the disclosure.

FIG. 11 illustrates a data flow that may be used to support narrowbandcommunications using narrowband TDD frame structures in accordance withcertain aspects of the disclosure.

FIGS. 12A-12C are a flowchart of a method of wireless communication.

FIGS. 13A-13C are a flowchart of a method of wireless communication.

FIGS. 14A and 14B are a flowchart of a method of wireless communication.

FIG. 15 is a flowchart of a method of wireless communication.

FIG. 16 is a flowchart of a method of wireless communication.

FIG. 17 is a flowchart of a method of wireless communication.

FIG. 18 is a conceptual data flow diagram illustrating the data flowbetween different means/components in an exemplary apparatus.

FIG. 19 is a diagram illustrating an example of a hardwareimplementation for an apparatus employing a processing system.

FIG. 20 is a flowchart of a method of wireless communication.

FIG. 21 is a flowchart of a method of wireless communication.

FIG. 22 is a flowchart of a method of wireless communication.

FIG. 23 is a conceptual data flow diagram illustrating the data flowbetween different means/components in an exemplary apparatus.

FIG. 24 is a diagram illustrating an example of a hardwareimplementation for an apparatus employing a processing system.

FIG. 25 is a conceptual data flow diagram illustrating the data flowbetween different means/components in an exemplary apparatus.

FIG. 26 is a diagram illustrating an example of a hardwareimplementation for an apparatus employing a processing system.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of various configurations and isnot intended to represent the only configurations in which the conceptsdescribed herein may be practiced. The detailed description includesspecific details for the purpose of providing a thorough understandingof various concepts. However, it will be apparent to those skilled inthe art that these concepts may be practiced without these specificdetails. In some instances, well known structures and components areshown in block diagram form in order to avoid obscuring such concepts.

Several aspects of telecommunication systems will now be presented withreference to various apparatus and methods. These apparatus and methodswill be described in the following detailed description and illustratedin the accompanying drawings by various blocks, components, circuits,processes, algorithms, etc. (collectively referred to as “elements”).These elements may be implemented using electronic hardware, computersoftware, or any combination thereof. Whether such elements areimplemented as hardware or software depends upon the particularapplication and design constraints imposed on the overall system.

By way of example, an element, or any portion of an element, or anycombination of elements may be implemented as a “processing system” thatincludes one or more processors. Examples of processors includemicroprocessors, microcontrollers, graphics processing units (GPUs),central processing units (CPUs), application processors, digital signalprocessors (DSPs), reduced instruction set computing (RISC) processors,systems on a chip (SoC), baseband processors, field programmable gatearrays (FPGAs), programmable logic devices (PLDs), state machines, gatedlogic, discrete hardware circuits, and other suitable hardwareconfigured to perform the various functionality described throughoutthis disclosure. One or more processors in the processing system mayexecute software. Software shall be construed broadly to meaninstructions, instruction sets, code, code segments, program code,programs, subprograms, software components, applications, softwareapplications, software packages, routines, subroutines, objects,executables, threads of execution, procedures, functions, etc., whetherreferred to as software, firmware, middleware, microcode, hardwaredescription language, or otherwise.

Accordingly, in one or more example embodiments, the functions describedmay be implemented in hardware, software, or any combination thereof. Ifimplemented in software, the functions may be stored on or encoded asone or more instructions or code on a computer-readable medium.Computer-readable media includes computer storage media. Storage mediamay be any available media that can be accessed by a computer. By way ofexample, and not limitation, such computer-readable media can comprise arandom-access memory (RAM), a read-only memory (ROM), an electricallyerasable programmable ROM (EEPROM), optical disk storage, magnetic diskstorage, other magnetic storage devices, combinations of theaforementioned types of computer-readable media, or any other mediumthat can be used to store computer executable code in the form ofinstructions or data structures that can be accessed by a computer.

FIG. 1 is a diagram illustrating an example of a wireless communicationssystem and an access network 100. The wireless communications system(also referred to as a wireless wide area network (WWAN)) includes basestations 102, UEs 104, and an Evolved Packet Core (EPC) 160. The basestations 102 may include macro cells (high power cellular base station)and/or small cells (low power cellular base station). The macro cellsinclude base stations. The small cells include femtocells, picocells,and microcells.

The base stations 102 (collectively referred to as Evolved UniversalMobile Telecommunications System (UMTS) Terrestrial Radio Access Network(E-UTRAN)) interface with the EPC 160 through backhaul links 132 (e.g.,S1 interface). In addition to other functions, the base stations 102 mayperform one or more of the following functions: transfer of user data,radio channel ciphering and deciphering, integrity protection, headercompression, mobility control functions (e.g., handover, dualconnectivity), inter-cell interference coordination, connection setupand release, load balancing, distribution for non-access stratum (NAS)messages, NAS node selection, synchronization, radio access network(RAN) sharing, multimedia broadcast multicast service (MBMS), subscriberand equipment trace, RAN information management (RIM), paging,positioning, and delivery of warning messages. The base stations 102 maycommunicate directly or indirectly (e.g., through the EPC 160) with eachother over backhaul links 134 (e.g., X2 interface). The backhaul links134 may be wired or wireless.

The base stations 102 may wirelessly communicate with the UEs 104. Eachof the base stations 102 may provide communication coverage for arespective geographic coverage area 110. There may be overlappinggeographic coverage areas 110. For example, the small cell 102′ may havea coverage area 110′ that overlaps the coverage area 110 of one or moremacro base stations 102. A network that includes both small cell andmacro cells may be known as a heterogeneous network. A heterogeneousnetwork may also include Home Evolved Node Bs (eNBs) (HeNBs), which mayprovide service to a restricted group known as a closed subscriber group(CSG). The communication links 120 between the base stations 102 and theUEs 104 may include uplink (UL) (also referred to as reverse link)transmissions from a UE 104 to a base station 102 and/or downlink (DL)(also referred to as forward link) transmissions from a base station 102to a UE 104. The communication links 120 may use multiple-input andmultiple-output (MIMO) antenna technology, including spatialmultiplexing, beamforming, and/or transmit diversity. The communicationlinks may be through one or more carriers. The base stations 102/UEs 104may use spectrum up to Y MHz (e.g., 5, 10, 15, 20, 100 MHz) bandwidthper carrier allocated in a carrier aggregation of up to a total of YxMHz (x component carriers) used for transmission in each direction. Thecarriers may or may not be adjacent to each other. Allocation ofcarriers may be asymmetric with respect to DL and UL (e.g., more or lesscarriers may be allocated for DL than for UL). The component carriersmay include a primary component carrier and one or more secondarycomponent carriers. A primary component carrier may be referred to as aprimary cell (PCell) and a secondary component carrier may be referredto as a secondary cell (SCell).

Certain UEs 104 may communicate with each other using device-to-device(D2D) communication link 192. The D2D communication link 192 may use theDL/UL WWAN spectrum. The D2D communication link 192 may use one or moresidelink channels, such as a physical sidelink broadcast channel(PSBCH), a physical sidelink discovery channel (PSDCH), a physicalsidelink shared channel (PSSCH), and a physical sidelink control channel(PSCCH). D2D communication may be through a variety of wireless D2Dcommunications systems, such as for example, FlashLinQ, WiMedia,Bluetooth, ZigBee, Wi-Fi based on the IEEE 802.11 standard, LTE, or NR.

The wireless communications system may further include a Wi-Fi accesspoint (AP) 150 in communication with Wi-Fi stations (STAs) 152 viacommunication links 154 in a 5 GHz unlicensed frequency spectrum. Whencommunicating in an unlicensed frequency spectrum, the STAs 152/AP 150may perform a clear channel assessment (CCA) prior to communicating inorder to determine whether the channel is available.

The small cell 102′ may operate in a licensed and/or an unlicensedfrequency spectrum. When operating in an unlicensed frequency spectrum,the small cell 102′ may employ NR and use the same 5 GHz unlicensedfrequency spectrum as used by the Wi-Fi AP 150. The small cell 102′,employing NR in an unlicensed frequency spectrum, may boost coverage toand/or increase capacity of the access network.

The gNodeB (gNB) 180 may operate in millimeter wave (mmW) frequenciesand/or near mmW frequencies in communication with the UE 104. When thegNB 180 operates in mmW or near mmW frequencies, the gNB 180 may bereferred to as an mmW base station. Extremely high frequency (EHF) ispart of the RF in the electromagnetic spectrum. EHF has a range of 30GHz to 300 GHz and a wavelength between 1 millimeter and 10 millimeters.Radio waves in the band may be referred to as a millimeter wave. NearmmW may extend down to a frequency of 3 GHz with a wavelength of 100millimeters. The super high frequency (SHF) band extends between 3 GHzand 30 GHz, also referred to as centimeter wave. Communications usingthe mmW/near mmW radio frequency band has extremely high path loss and ashort range. The mmW base station 180 may utilize beamforming 184 withthe UE 104 to compensate for the extremely high path loss and shortrange.

The EPC 160 may include a Mobility Management Entity (MME) 162, otherMMEs 164, a Serving Gateway 166, a Multimedia Broadcast MulticastService (MBMS) Gateway 168, a Broadcast Multicast Service Center (BM-SC)170, and a Packet Data Network (PDN) Gateway 172. The MME 162 may be incommunication with a Home Subscriber Server (HSS) 174. The MME 162 isthe control node that processes the signaling between the UEs 104 andthe EPC 160. Generally, the MME 162 provides bearer and connectionmanagement. All user Internet protocol (IP) packets are transferredthrough the Serving Gateway 166, which itself is connected to the PDNGateway 172. The PDN Gateway 172 provides UE IP address allocation aswell as other functions. The PDN Gateway 172 and the BM-SC 170 areconnected to the IP Services 176. The IP Services 176 may include theInternet, an intranet, an IP Multimedia Subsystem (IMS), a PS StreamingService, and/or other IP services. The BM-SC 170 may provide functionsfor MBMS user service provisioning and delivery. The BM-SC 170 may serveas an entry point for content provider MBMS transmission, may be used toauthorize and initiate MBMS Bearer Services within a public land mobilenetwork (PLMN), and may be used to schedule MBMS transmissions. The MBMSGateway 168 may be used to distribute MBMS traffic to the base stations102 belonging to a Multicast Broadcast Single Frequency Network (MBSFN)area broadcasting a particular service, and may be responsible forsession management (start/stop) and for collecting eMBMS relatedcharging information.

The base station may also be referred to as a gNB, Node B, evolved NodeB (eNB), an access point, a base transceiver station, a radio basestation, a radio transceiver, a transceiver function, a basic serviceset (BSS), an extended service set (ESS), or some other suitableterminology. The base station 102 provides an access point to the EPC160 for a UE 104. Examples of UEs 104 include a cellular phone, a smartphone, a session initiation protocol (SIP) phone, a laptop, a personaldigital assistant (PDA), a satellite radio, a global positioning system,a multimedia device, a video device, a digital audio player (e.g., MP3player), a camera, a game console, a tablet, a smart device, a wearabledevice, a vehicle, an electric meter, a gas pump, a large or smallkitchen appliance, a healthcare device, an implant, a display, or anyother similar functioning device. Some of the UEs 104 may be referred toas IoT devices (e.g., parking meter, gas pump, toaster, vehicles, heartmonitor, etc.). The UE 104 may also be referred to as a station, amobile station, a subscriber station, a mobile unit, a subscriber unit,a wireless unit, a remote unit, a mobile device, a wireless device, awireless communications device, a remote device, a mobile subscriberstation, an access terminal, a mobile terminal, a wireless terminal, aremote terminal, a handset, a user agent, a mobile client, a client, orsome other suitable terminology.

Referring again to FIG. 1, in certain aspects, the base station 102 maybe configured to support one or more narrowband TDD frame structure(s)for narrowband communications (198), e.g., corresponding to FIGS. 4-26.

FIG. 2A is a diagram 200 illustrating an example of a DL frame structurein LTE. FIG. 2B is a diagram 230 illustrating an example of channelswithin the DL frame structure in LTE. FIG. 2C is a diagram 250illustrating an example of an UL frame structure in LTE. FIG. 2D is adiagram 280 illustrating an example of channels within the UL framestructure in LTE. Other wireless communication technologies may have adifferent frame structure and/or different channels. In LTE, a frame (10ms) may be divided into 10 equally sized subframes. Each subframe mayinclude two consecutive time slots. A resource grid may be used torepresent the two time slots, each time slot including one or more timeconcurrent resource blocks (RBs) (also referred to as physical RBs(PRBs)). The resource grid is divided into multiple resource elements(REs). In LTE, for a normal cyclic prefix, an RB contains 12 consecutivesubcarriers in the frequency domain and 7 consecutive symbols (for DL,OFDM symbols; for UL, SC-FDMA symbols) in the time domain, for a totalof 84 REs. For an extended cyclic prefix, an RB contains 12 consecutivesubcarriers in the frequency domain and 6 consecutive symbols in thetime domain, for a total of 72 REs. The number of bits carried by eachRE depends on the modulation scheme.

As illustrated in FIG. 2A, some of the REs carry DL reference (pilot)signals (DL-RS) for channel estimation at the UE. The DL-RS may includecell-specific reference signals (CRS) (also sometimes called common RS),UE-specific reference signals (UE-RS), and channel state informationreference signals (CSI-RS). FIG. 2A illustrates CRS for antenna ports 0,1, 2, and 3 (indicated as R₀, R₁, R₂, and R₃, respectively), UE-RS forantenna port 5 (indicated as R₅), and CSI-RS for antenna port 15(indicated as R). FIG. 2B illustrates an example of various channelswithin a DL subframe of a frame. The physical control format indicatorchannel (PCFICH) is within symbol 0 of slot 0, and carries a controlformat indicator (CFI) that indicates whether the physical downlinkcontrol channel (PDCCH) occupies 1, 2, or 3 symbols (FIG. 2B illustratesa PDCCH that occupies 3 symbols). The PDCCH carries downlink controlinformation (DCI) within one or more control channel elements (CCEs),each CCE including nine RE groups (REGs), each REG including fourconsecutive REs in an OFDM symbol. A UE may be configured with aUE-specific enhanced PDCCH (ePDCCH) that also carries DCI. The ePDCCHmay have 2, 4, or 8 RB pairs (FIG. 2B shows two RB pairs, each subsetincluding one RB pair). The physical hybrid automatic repeat request(ARQ) (HARQ) indicator channel (PHICH) is also within symbol 0 of slot 0and carries the HARQ indicator (HI) that indicates HARQ acknowledgement(ACK)/negative ACK (NACK) feedback based on the physical uplink sharedchannel (PUSCH). The primary synchronization channel (PSCH) is withinsymbol 6 of slot 0 within subframes 0 and 5 of a frame, and carries aPSS that is used by a UE to determine subframe timing and a physicallayer identity. The secondary synchronization channel (SSCH) is withinsymbol 5 of slot 0 within subframes 0 and 5 of a frame, and carries anSSS that is used by a UE to determine a physical layer cell identitygroup number. Based on the physical layer identity and the physicallayer cell identity group number, the UE can determine a physical cellidentifier (PCI). Based on the PCI, the UE can determine the locationsof the aforementioned DL-RS. The physical broadcast channel (PBCH) iswithin symbols 0, 1, 2, 3 of slot 1 of subframe 0 of a frame, andcarries a master information block (MIB). The MIB provides a number ofRBs in the DL system bandwidth, a PHICH configuration, and a systemframe number (SFN). The physical downlink shared channel (PDSCH) carriesuser data, broadcast system information not transmitted through the PBCHsuch as system information blocks (SIBs), and paging messages.

As illustrated in FIG. 2C, some of the REs carry demodulation referencesignals (DM-RS) for channel estimation at the eNB. The UE mayadditionally transmit sounding reference signals (SRS) in the lastsymbol of a subframe. The SRS may have a comb structure, and a UE maytransmit SRS on one of the combs. The SRS may be used by an eNB forchannel quality estimation to enable frequency-dependent scheduling onthe UL. FIG. 2D illustrates an example of various channels within an ULsubframe of a frame. A physical random access channel (PRACH) may bewithin one or more subframes within a frame based on the PRACHconfiguration. The PRACH may include six consecutive RB pairs within asubframe. The PRACH allows the UE to perform initial system access andachieve UL synchronization. A physical uplink control channel (PUCCH)may be located on edges of the UL system bandwidth. The PUCCH carriesuplink control information (UCI), such as scheduling requests, a channelquality indicator (CQI), a precoding matrix indicator (PMI), a rankindicator (RI), and HARQ ACK/NACK feedback. The PUSCH carries data, andmay additionally be used to carry a buffer status report (BSR), a powerheadroom report (PHR), and/or UCI.

FIG. 3 is a block diagram of an eNB 310 in communication with a UE 350in an access network. In the DL, IP packets from the EPC 160 may beprovided to a controller/processor 375. The controller/processor 375implements layer 3 and layer 2 functionality. Layer 3 includes a radioresource control (RRC) layer, and layer 2 includes a packet dataconvergence protocol (PDCP) layer, a radio link control (RLC) layer, anda medium access control (MAC) layer. The controller/processor 375provides RRC layer functionality associated with broadcasting of systeminformation (e.g., MIB, SIBs), RRC connection control (e.g., RRCconnection paging, RRC connection establishment, RRC connectionmodification, and RRC connection release), inter radio access technology(RAT) mobility, and measurement configuration for UE measurementreporting; PDCP layer functionality associated with headercompression/decompression, security (ciphering, deciphering, integrityprotection, integrity verification), and handover support functions; RLClayer functionality associated with the transfer of upper layer packetdata units (PDUs), error correction through ARQ, concatenation,segmentation, and reassembly of RLC service data units (SDUs),re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; andMAC layer functionality associated with mapping between logical channelsand transport channels, multiplexing of MAC SDUs onto transport blocks(TBs), demultiplexing of MAC SDUs from TBs, scheduling informationreporting, error correction through HARQ, priority handling, and logicalchannel prioritization.

The transmit (TX) processor 316 and the receive (RX) processor 370implement layer 1 functionality associated with various signalprocessing functions. Layer 1, which includes a physical (PHY) layer,may include error detection on the transport channels, forward errorcorrection (FEC) coding/decoding of the transport channels,interleaving, rate matching, mapping onto physical channels,modulation/demodulation of physical channels, and MIMO antennaprocessing. The TX processor 316 handles mapping to signalconstellations based on various modulation schemes (e.g., binaryphase-shift keying (BPSK), quadrature phase-shift keying (QPSK),M-phase-shift keying (M-PSK), M-quadrature amplitude modulation(M-QAM)). The coded and modulated symbols may then be split intoparallel streams. Each stream may then be mapped to an OFDM subcarrier,multiplexed with a reference signal (e.g., pilot) in the time and/orfrequency domain, and then combined together using an Inverse FastFourier Transform (IFFT) to produce a physical channel carrying a timedomain OFDM symbol stream. The OFDM stream is spatially precoded toproduce multiple spatial streams. Channel estimates from a channelestimator 374 may be used to determine the coding and modulation scheme,as well as for spatial processing. The channel estimate may be derivedfrom a reference signal and/or channel condition feedback transmitted bythe UE 350. Each spatial stream may then be provided to a differentantenna 320 via a separate transmitter 318TX. Each transmitter 318TX maymodulate an RF carrier with a respective spatial stream fortransmission.

At the UE 350, each receiver 354RX receives a signal through itsrespective antenna 352. Each receiver 354RX recovers informationmodulated onto an RF carrier and provides the information to the receive(RX) processor 356. The TX processor 368 and the RX processor 356implement layer 1 functionality associated with various signalprocessing functions. The RX processor 356 may perform spatialprocessing on the information to recover any spatial streams destinedfor the UE 350. If multiple spatial streams are destined for the UE 350,they may be combined by the RX processor 356 into a single OFDM symbolstream. The RX processor 356 then converts the OFDM symbol stream fromthe time-domain to the frequency domain using a Fast Fourier Transform(FFT). The frequency domain signal comprises a separate OFDM symbolstream for each subcarrier of the OFDM signal. The symbols on eachsubcarrier, and the reference signal, are recovered and demodulated bydetermining the most likely signal constellation points transmitted bythe eNB 310. These soft decisions may be based on channel estimatescomputed by the channel estimator 358. The soft decisions are thendecoded and deinterleaved to recover the data and control signals thatwere originally transmitted by the eNB 310 on the physical channel. Thedata and control signals are then provided to the controller/processor359, which implements layer 3 and layer 2 functionality.

The controller/processor 359 can be associated with a memory 360 thatstores program codes and data. The memory 360 may be referred to as acomputer-readable medium. In the UL, the controller/processor 359provides demultiplexing between transport and logical channels, packetreassembly, deciphering, header decompression, and control signalprocessing to recover IP packets from the EPC 160. Thecontroller/processor 359 is also responsible for error detection usingan ACK and/or NACK protocol to support HARQ operations.

Similar to the functionality described in connection with the DLtransmission by the eNB 310, the controller/processor 359 provides RRClayer functionality associated with system information (e.g., MIB, SIBs)acquisition, RRC connections, and measurement reporting; PDCP layerfunctionality associated with header compression/decompression, andsecurity (ciphering, deciphering, integrity protection, integrityverification); RLC layer functionality associated with the transfer ofupper layer PDUs, error correction through ARQ, concatenation,segmentation, and reassembly of RLC SDUs, re-segmentation of RLC dataPDUs, and reordering of RLC data PDUs; and MAC layer functionalityassociated with mapping between logical channels and transport channels,multiplexing of MAC SDUs onto TBs, demultiplexing of MAC SDUs from TBs,scheduling information reporting, error correction through HARQ,priority handling, and logical channel prioritization.

Channel estimates derived by a channel estimator 358 from a referencesignal or feedback transmitted by the eNB 310 may be used by the TXprocessor 368 to select the appropriate coding and modulation schemes,and to facilitate spatial processing. The spatial streams generated bythe TX processor 368 may be provided to different antenna 352 viaseparate transmitters 354TX. Each transmitter 354TX may modulate an RFcarrier with a respective spatial stream for transmission.

The UL transmission is processed at the eNB 310 in a manner similar tothat described in connection with the receiver function at the UE 350.Each receiver 318RX receives a signal through its respective antenna320. Each receiver 318RX recovers information modulated onto an RFcarrier and provides the information to a RX processor 370.

The controller/processor 375 can be associated with a memory 376 thatstores program codes and data. The memory 376 may be referred to as acomputer-readable medium. In the UL, the controller/processor 375provides demultiplexing between transport and logical channels, packetreassembly, deciphering, header decompression, control signal processingto recover IP packets from the UE 350. IP packets from thecontroller/processor 375 may be provided to the EPC 160. Thecontroller/processor 375 is also responsible for error detection usingan ACK and/or NACK protocol to support HARQ operations.

Narrowband communications involve communicating with a limited frequencybandwidth as compared to the frequency bandwidth used for LTEcommunications. One example of narrowband communication is NB-IoTcommunication, which is limited to a single RB of system bandwidth,e.g., 180 kHz. Another example of narrowband communication is eMTC,which is limited to six RBs of system bandwidth, e.g., 1.08 MHz.

NB-IoT communication and eMTC may reduce device complexity, enablemulti-year battery life, and provide deeper coverage to reachchallenging locations such as deep inside buildings. However, becausethe coverage provided by narrowband communications may include reachingchallenging locations (e.g., a smart gas meter located in the basementof a building), there is an increased chance that one or moretransmissions will not be properly decoded by a receiver device.Consequently, narrowband communication may include a predeterminednumber of repeated transmissions to increase the chance of having thetransmission properly decoded by the receiver device. A TDD framestructure may be used by a narrowband communication system since certainTDD frame configurations may include a greater number of contiguousuplink and/or downlink subframes that may be used for the repeatedtransmissions, as compared to a FDD frame structure. There is a need tosupport the use of narrowband TDD frame structure for narrowbandcommunication.

The present disclosure provides a solution by supporting NPDCCH, NPDSCH,NPUCCH, and/or NPUSCH transmissions that use a narrowband TDD framestructure, e.g., as described below with reference below to FIGS. 5-28.

FIG. 4 is a diagram illustrating a narrowband TDD frame structure 400that may be determined for narrowband communications in accordance withcertain aspects of the disclosure. In certain aspects, the narrowbandTDD frame structure 400 may be determined from the group of narrowbandTDD frame structures (e.g., configuration 0-configuration o) listed intable 410. For example, a base station may determine the narrowband TDDframe structure based on higher layer signaling (e.g., RRC messaging)received from the network. Additionally and/or alternatively, the basestation may determine the narrowband TDD frame structure based onchannel conditions.

In one aspect, the narrowband TDD frame structure 400 may include a 10ms frame split into two half frames, each 5 ms long. The half-frames maybe further split into five subframes, each 1 ms long. The narrowband TDDframe structure 400 may include any one of the narrowband configurationslisted in table 410.

Switching periodicity refers to the time a UE may use to switch betweenmonitoring a downlink subframe (e.g., for downlink transmissions from abase station) and sending a transmission using an uplink subframe, orvice versa. Depending on the determined narrowband TDD frame structure400, the switching periodicity may be 5 ms, 10 ms, or more than 10 ms(e.g., 20 ms). For narrowband TDD frame structures 412 (e.g.,configurations 0-2 and 6) with a 5 ms switching periodicity, a specialsubframe (SSF) may exist in both half frames of the narrowband TDD framestructure 400. For narrowband TDD frame structures 414 (e.g.,configurations 3-5) with a 10 ms switching periodicity, the specialsubframe may exist in the first half frame but not in the second halfframe. For narrowband TDD frame structures 416 (e.g., configurations/ando) with more than a 10 ms switching periodicity, no special subframesmay be needed since more than an entire frame may be used to perform theswitch. In the narrowband TDD frame structures 412, 414 that include aspecial subframe (e.g., configurations 0, 1, 2, 3, 4, 5, and 6),subframes 0 and 5, as well as the Downlink Pilot Time Slot (DwPTS) inthe special subframe, may be reserved for downlink transmissions.Additionally and/or alternatively, in the narrowband TDD framestructures 412, 414 that include a special subframe, the Uplink PilotTime Slot (UpPTS) in the special subframe and the subframe immediatelyfollowing the special subframe may be reserved for the uplinktransmission.

When operating in in-band mode and/or guard-band mode, the narrowbandTDD frame structure 400 may reuse certain LTE TDD frame structures(e.g., see configurations 0, 1, 2, 3, 4, 5, 6 in FIG. 4). Additionallyand/or alternatively, some subframes in the narrowband TDD framestructure 400 may be marked as flexible subframes (e.g., seeconfiguration/and o in FIG. 4). A UE may use a flexible subframe aseither a downlink subframe or an uplink subframe depending on thecurrent grant received from the base station.

In certain aspects, a subset of the narrowband TDD configurations listedin table 410 in FIG. 4 may be used to support narrowband communications.For example, configuration 0 may not be suitable for narrowbandcommunications because configuration 0 only has two downlink subframes.In one configuration, narrowband communications that use a narrowbandTDD frame structure may be supported in in-band mode and/or guard-bandmode (e.g., but not standalone mode). In another configuration,narrowband communications that use a narrowband TDD frame structure maysupport in-band mode, guard-band mode, and standalone mode.

In addition, multiple narrowband downlink carriers and multiplenarrowband uplink carriers may be used to enhance narrowbandcommunication between a base station and a UE. Among the carriers, anarrowband anchor carrier may be used to provide synchronization, systeminformation, paging, data and control for multi-carrier enabled UEs.Hence, overhead narrowband system information may be reduced when anarrowband anchor carrier is used. Synchronization and paging for acertain cell may not be not provided on all narrowband carriers.Narrowband carriers that do not provide synchronization and/or pagingmay be referred to narrowband non-anchor carriers. Coordination betweenbase stations for selecting anchor carriers that mitigate interferenceand for transmit power control for non-anchor carriers provide furthernetwork performance advantages.

NPDCCH and/or NPDSCH on Special Subframes

While narrowband FDD frame structures may include resources for downlinktransmissions in downlink subframes, certain narrowband TDD framestructures may include resources for downlink transmissions in bothdownlink subframes and special subframes. For example, the DwPTS portionof a special subframe includes resources that may be allocated fordownlink transmissions. In some scenarios, there is a need to determineif the resources in the DwPTS portion of special subframes may beallocated for the NPDCCH and/or NPDSCH to efficiently use the availableresources in the narrowband TDD frame structure.

FIG. 5 illustrates a data flow 500 that may be used to allocateresources for the NPDCCH and/or NPDSCH in downlink subframes as well asspecial subframes in accordance with certain aspects of the disclosure.Base station 504 may correspond to, e.g., base station 102, 180, 604,704, 804, 904, 1004, 1104, 2350, eNB 310, apparatus 1802/1802′,2502/2502′. UE 506 may correspond to, e.g., UE 104, 350, 606, 706, 806,906, 1006, 1106, 1850, 2550, apparatus 2302/2302′. In addition, the basestation 504 and the UE 506 may be configured to communicate usingnarrowband communications (e.g., NB-IoT and/or eMTC). For example, theUE 506 may be an NB-IoT device and/or an eMTC device, and base station504 may be able to transmit a NPDCCH and/or NPDSCH in one or moredownlink subframes as well as special subframes (e.g., in the DwPTSportion of the special subframes).

In one aspect, base station 504 may determine 501 to transmit an NPDCCHand/or NPDSCH in a subframe in a narrowband TDD frame structure. Forexample, the base station 504 may determine 501 the narrowband TDD framestructure is one of configuration 0, 1, 2, 3, 4, 5, 6, 1, or o fromtable 410 in FIG. 4.

In addition, base station 504 may determine 503 whether a subframeallocated for an NPDCCH and/or NPDSCH is a special subframe or adownlink subframe when the determined narrowband TDD frame structureincludes one or more special subframes (e.g., configurations 0, 1, 2, 3,4, 5, 6, and n in FIG. 4).

In another aspect, base station 504 may determine 505 how to transmitthe NPDCCH and/or NPDSCH, and how to allocate resources in one or moredownlink subframe and/or special subframes. In one aspect, the basestation 504 may allocate resources for the NPDCCH and/or NPDSCH in allavailable downlink subframes (e.g., downlink subframes not being usedfor switching). However, the allocation of resources on a specialsubframe by base station 504 may be a function of a special subframeconfiguration (e.g., how many resources are available in the DwPTSportion) and/or the determined narrowband TDD frame.

In a first configuration, base station 504 may determine 505 to transmitthe NPDCCH and/or NPDSCH in downlink subframes and not specialsubframes. In the first configuration, base station 504 may not allocateresources for the NPDCCH and/or NPDSCH on special subframes. If arepetition of the NPDCCH and/or NPDSCH is configured at the base station504, an allocation of resources may be postponed at special subframes inthe narrowband TDD frame structure until the next possible downlinksubframe. Assuming configuration 2 is used as the narrowband TDD framestructure, resources may be allocated for the NPDCCH and/or NPDSCH onsubframe 0 and postponed at subframe 1 until subframe 3 (e.g., resourceallocation is postposed at special subframe 1 until the next downlinksubframe 3). Hence, the base station 504 may transmit the NPDCCH 507and/or NPDSCH 507 in subframe 0, and a repetition of the NPDCCH 511and/or NPDSCH 511 may be transmitted in subframe 3 (e.g., the nextdownlink subframe in configuration 2).

In a second configuration, base station 504 may determine 505 totransmit the NPDCCH 507, 509 and/or NPDSCH 507, 509 in downlinksubframes (e.g., NPDCCH 507 and/or NPDSCH 509) and special subframes(e.g., NPDCCH 509 and/or NPDSCH 509). In the second configuration, thebase station 504 may allocate resources for the NPDCCH and/or NPDSCH indownlink subframes as well as the DwPTS portion of one or more specialsubframes.

In a first aspect of the second configuration, base station 504 maypuncture the OFDM symbols in the UpPTS portion of the one or morespecial subframes.

In a second aspect of the second configuration, base station 504 maypuncture the OFDM symbols in the DwPTS portion and the UpPTS portion ofthe one or more special subframes. By puncturing the OFDM symbols in theDwPTS portion and the UpPTS portion of the one or more specialsubframes, UE 506 may ignore (e.g., not monitor or discard) the specialsubframes while receiving NPDCCH and/or NPDSCH in a radio frame.

In a third aspect of the second configuration, base station 504 may ratematch the NPDCCH and/or NPDSCH in the subframe (e.g., downlink subframeor special subframe) based on the number of downlink OFDM symbols in thesubframe. A special subframe may have a fewer number of OFDM symbolsthan a downlink subframe because only the DwPTS portion of the specialsubframe is dedicated for an NPDCCH and/or NPDSCH. Hence, the ratematching for a special subframe may be different than the rate matchingfor a downlink subframe.

In a third configuration, base station 504 may determine 505 to transmitthe NPDCCH 509 and/or NPDSCH 509 in a special subframe when a number ofOFDM symbols in the special subframe is greater than a predeterminedthreshold. Otherwise, base station 504 may transmit a repetition of theNPDCCH 511 and/or NPDCCH 511 in the next downlink subframe. As anillustrative example, assume configuration 2 is used for the narrowbandTDD frame structure, that special subframe 1 has ten OFDM symbols, andthat the predetermined threshold is five OFDM symbols. Here, basestation 504 may transmit the NPDCCH 509 and/or NPDSCH 509 in subframe 0and a repetition of the NPDCCH 511 and/or NPDSCH 511 in special subframe1.

In a fourth configuration, base station 504 may determine 505 totransmit the NPDCCH 509 and/or NPDSCH 509 in the special subframe when anumber of OFDM symbols in the special subframe is less than apredetermined threshold. In the fourth configuration, base station 504may transmit the NPDCCH 509 and/or NPDSCH 509 with a subset of OFDMsymbols (e.g., a subset of the OFDM symbols in the DwPTS portion and/orthe UpPTS portion) punctured in the special subframe. As an illustrativeexample, assume configuration 2 is used for the narrowband TDD framestructure, that special subframe 1 has five OFDM symbols, and that thepredetermined threshold is ten OFDM symbols. Here, base station 504 maytransmit the NPDCCH 509 and/or NPDSCH 509 in subframe 0 and transmit arepetition of the NPDCCH 511 and/or NPDSCH 511 in special subframe 1with a subset of the OFDM symbols in special subframe 1 punctured.

In a fifth configuration, base station 504 may determine 505 to refrainfrom transmitting the NPDCCH and/or NPDSCH in a special subframe when anumber of OFDM symbols in the special subframe is less than apredetermined threshold. In the fifth configuration, base station 504may transmit the NPDCCH 511 and/or NPDSCH 511 in the next availabledownlink subframe. As an illustrative example, assume configuration 2 isused for the narrowband TDD frame structure, that special subframe 1 hasfive OFDM symbols, and that the predetermined threshold is ten OFDMsymbols. Here, base station 504 may transmit the NPDCCH 509 and/orNPDSCH 509 in subframe 0 and wait until the next downlink subframe 3 totransmit a repetition of the NPDCCH 511 and/or NPDSCH 511.

In a sixth configuration, base station 504 may determine 505 to drop thetransmission of the NPDCCH and/or NPDSCH in a special subframe when anumber of OFDM symbols in the special subframe is less than apredetermined threshold.

UE-RS

Channel reciprocity may occur when a downlink channel and an uplinkchannel are transmitted on the same channel or bandwidth. Using anarrowband TDD frame structure, downlink channel transmissions anduplink channel transmissions may occur on the same narrowband, and hencechannel reciprocity may be applicable. Channel reciprocity may beexploited to enable UE-specific beamforming that may be unavailable whena narrowband FDD frame structure is used.

Beamforming may be desirable in narrowband communication to compensatefor path loss that may occur when a UE is in a location that isdifficult for a signal to reach. For example, heavy attenuation mayoccur when a signal needs to reach a UE located deep inside a buildingdue to the presence of obstacles (e.g., walls, furniture, people, etc.)that may block the propagation of the signal. As such, propagationcharacteristics in narrowband communications may benefit fromdirectional beamforming that focuses the transmit energy in specificspatial directions corresponding to the dominant spatial scatterers,reflectors, and/or diffraction paths to overcome the signal loss at theUE. Beamforming may be implemented via an array of antennas (e.g.,phased arrays) cooperating to beamform a high frequency signal in aparticular direction of the UE, and therefore, extend the range of thesignal.

FIGS. 6A and 6B illustrate a data flow 600 that may be used to supportUE-specific beamforming in accordance with certain aspects of thedisclosure. Base station 504 may correspond to, e.g., base station 102,180, 604, 704, 804, 904, 1004, 1104, 2350, eNB 310, apparatus1802/1802′, 2502/2502′. UE 506 may correspond to, e.g., UE 104, 350,606, 706, 806, 906, 1006, 1106, 1850, 2550, apparatus 2302/2302′. Inaddition, the base station 604 and the UE 606 may be configured tocommunicate using narrowband communications (e.g., NB-IoT and/or eMTC),beamforming, and/or precoding. For example, the UE 606 may be an NB-IoTdevice and/or an eMTC device.

Referring to FIG. 6A, base station 604 may determine 601 a narrowbandTDD frame structure (e.g., configuration 0, 1, 2, 3, 4, 5, 6, 1, or olisted in table 410 in FIG. 4.) is used for narrowband communicationswith UE 606.

To perform beamforming, base station 604 may allocate 603 at least oneRB in the narrowband TDD frame structure for transmitting an NPDCCHand/or NPDSCH to UE 606, map 605 a UE-RS to the at least one RBallocated for the NPDCCH and/or NPDSCH, and transmit the UE-RS 607 tothe UE 606 based on the mapping (at 605). In one aspect, base station604 may use a legacy pilot structure (e.g., legacy port 5 pilotstructure, modified legacy port 107/108 pilot structure, modified legacyport 109/110 pilot structure, etc.) to populate the UE-RS 607.

In certain configurations, the UE-RS 607 may not share resources with anarrowband reference signal (NRS) 613 (e.g., seen in FIG. 6B) in thelegacy pilot structure. For example, the network (e.g., higher layers)may indicate certain downlink subframes that do not include NRS 613. Ifthe NPDCCH and/or NPDSCH is transmitted in subframes that do not includeNRS 613, base station 604 may transmit UE-RS 607 in the same REs as theNRS 613. Optionally, SRS may be used by the network to further supportmeasurements for channel reciprocity. If multi-user MIMO capability issupported (e.g. if two UEs are allocated by base station 604 to the sameRB for NPDCCH and/or NPDSCH), the legacy port 107/108 pilot structure orlegacy port 109/110 pilot structure may be reused.

In one aspect, UE 606 may use the UE-RS 607 to perform channelestimation (e.g., of the channel used to transmit the UE-RS 607 by basestation 604). Based on a result of the channel estimation, base station604 may receive a first channel estimate 609 associated with the UE-RS607 transmitted from the UE 606. In one aspect, base station 604 mayperform 611 a beamforming procedure using the first channel estimate 609received from the UE 606.

Referring to FIG. 6B, base station 604 may transmit an NRS 613 to UE606, and receive a second channel estimate 615 associated with the NRS613 from UE 606. In addition, UE 606 may combine the NRS 613 transmittedfrom each transmit antenna (e.g., port) at the base station 604 toenhance channel estimation (e.g. the second channel estimate 615).

Base station 604 may use the second channel estimate to determine 617 aprecoding for each of a plurality of transmit antennas used to transmitthe NPDCCH and/or NPDSCH.

In one configuration, base station 604 may signal 619 that each of themultiple transmit antennas are associated with the same precoding. Incertain configurations, the signal 619 may indicate that the NRS 613uses the same precoding for a predetermined number of radio frames(e.g., ten 10 radio frames) before switching to another precoding. Inone aspect, the signal 619 may be sent as DCI or RRC messaging. In oneconfiguration, the signal 619 may indicate that the NPDCCH istransmitted using a first number of antennas (e.g., one, two, three,etc.) and the NPDSCH is transmitted from a second number of antennas(e.g., one, two, three, etc.).

In one configuration, the NPDCCH 621 and/or NPDSCH 621 may betransmitted by base station 604 using a data stream from each of thetransmit antennas based on the beamforming and/or precoding. Theprecoding may be applied to a narrowband carrier (e.g., non-anchorcarrier) specific to UE 606.

ACK/NACK

FIGS. 7A and 7B illustrate a data flow 700 that may be used toaccommodate ACK/NACK transmissions when a narrowband TDD frame structureis in accordance with certain aspects of the disclosure. Base station504 may correspond to, e.g., base station 102, 180, 604, 704, 804, 904,1004, 1104, 2350, eNB 310, apparatus 1802/1802′, 2502/2502′. UE 506 maycorrespond to, e.g., UE 104, 350, 606, 706, 806, 906, 1006, 1106, 1850,2550, apparatus 2302/2302′. In addition, the base station 704 and the UE706 may be configured to communicate using narrowband communications(e.g., NB-IoT and/or eMTC). For example, the UE 706 may be an NB-IoTdevice and/or an eMTC device.

Referring to FIG. 7A, base station 704 may determine 701 to transmit anNPDCCH and/or NPDSCH using a subframe in a narrowband TDD framestructure. For example, the base station 704 may determine 701 thenarrowband TDD frame structure is one of configuration 0, 1, 2, 3, 4, 5,6, 1, or o from table 410 in FIG. 4.

In one configuration, base station 704 may determine 703 a first set ofsubframes in the narrowband TDD frame structure used to transmit theNPDCCH to UE 706. For example, a last subframe in the first set ofsubframes may be subframe n. In addition, base station 704 may schedule705 a first uplink subframe in the narrowband TDD frame structure forthe UE 706 to report a first ACK/NACK associated with the NPDCCH. In oneconfiguration, the first uplink subframe may be delayed based on k₀number of subframes after the last subframe n. In other words, UE 706may transmit the first ACK/NACK in subframe n+k₀. Information 707associated with the k₀ number of subframes may be signaled to UE 706 ina first delay field in a DCI transmission (e.g. not shown in FIGS. 7Aand 7B).

As an illustrative example, assume that configuration 2 (e.g., see table410 in FIG. 4) is used as the narrowband TDD frame structure. Inaddition, assume that the first set of subframes used to transmit theNPDCCH includes subframes 0 and 1 (e.g., n is equal to 1), and that k₀is equal to 1. Hence in the illustrative example, the first ACK/NACKassociated with the NPDCCH may be transmitted by UE 706 in subframe 2(e.g., 1+1=2) of the narrowband TDD frame structure.

In addition, base station 704 may determine 709 a second set ofsubframes in the narrowband TDD frame structure used to transmit theNPDSCH to UE 706. In one aspect, a first subframe in the second set ofsubframes may be located x number of subframes after the subframeallocated for the first ACK/NACK transmission. For example, the firstsubframe in the second set of subframes is subframe n+k₀+x. A lastsubframe in the second set of subframes may be y subframes after thefirst subframe in the second set. For example, the last subframe in thesecond set of subframes may be subframe n+k₀+x+y. Both x and y may bepositive integers.

Referring to FIG. 7B, base station 704 may schedule 711 a second uplinksubframe in the narrowband TDD frame structure for the UE 706 to reporta second ACK/NACK associated with the NPDSCH. In one aspect, the seconduplink subframe may be delayed m₀ number of subframes after the lastsubframe used to transmit the NPDSCH (e.g., subframe n+k₀+x+y), and them₀ number of subframes may include at least one of a number of downlinksubframes and/or a number of uplink subframes. Information 713associated with the m₀ number of subframes may be signaled to UE 706 ina second delay field in the DCI transmission. In one configuration, theinformation 707, 713 may be signaled in the same DCI transmission. Inanother configuration, the information 707, 713 may be signaled indifferent DCI transmissions.

Referring again to the illustrative example discussed above for FIGS. 7Aand 7B, further assume that the second set of subframes are subframes 3,4, and 5 in configuration 2. In the example, x is equal to 1 and y isequal to 2. In a first scenario, assume m₀ is equal to 3 when onlydownlink subframes are included in the delayed number of subframes. In asecond scenario, assume m₀ is equal to 4 when downlink subframes anduplink subframes are included in the delayed number of subframes. Ineither scenario, the second ACK/NACK associated with the NPDSCH may betransmitted by UE 706 in subframe 2 in the next radio frame after theradio frame in which the NPDSCH is received by UE 706. Additionallyand/or alternatively, m₀ may only include valid uplink subframes and/ordownlink subframes (e.g., subframes available for transmission and notswitching).

In certain configurations, base station 704 may receive a bundle 715including a plurality of ACK/NACKs from UE 706. In one aspect, eachACK/NACK in the bundle may be associated with a different hybridautomatic repeat request (HARQ) process associated with one or moreNPDCCH transmissions and/or NPDSCH transmissions.

Uplink and Downlink Transmission Interlacing

FIGS. 8A-8C illustrate a data flows 800, 854, 855 that may enableinterlacing of uplink subframes and downlink subframes during NPDSCHand/or narrowband physical uplink shared channel (NPUSCH) transmissions.For example, FIG. 8A illustrates a data flow 800 in which interlacing isnot enabled. FIG. 8B illustrates a data flow 845 in which interlacingmay be enabled and NPUSCH transmissions may be restricted to certainsubframes. FIG. 8C illustrates a data flow 855 in which interlacing maybe enabled and monitoring for NPDSCH transmissions may be restricted tocertain subframes.

Base station 504 may correspond to, e.g., base station 102, 180, 604,704, 804, 904, 1004, 1104, 2350, eNB 310, apparatus 1802/1802′,2502/2502′. UE 506 may correspond to, e.g., UE 104, 350, 606, 706, 806,906, 1006, 1106, 1850, 2550, apparatus 2302/2302′. In addition, the basestation 804 and the UE 806 may be configured to communicate usingnarrowband communications (e.g., NB-IoT and/or eMTC). For example, theUE 806 may be an NB-IoT device and/or an eMTC device.

Referring to FIG. 8A, UE 806 may receive information 801 indicating anarrowband TDD frame structure from base station 804. For example, theinformation 801 may indicate that the narrowband TDD frame structure isone of configuration 0, 1, 2, 3, 4, 5, 6, 1, or o from table 410 in FIG.4.

In addition, UE 806 may monitor 803 one or more downlink subframes for adownlink transmission (e.g., NPDCCH and/or NPDSCH) in a first radioframe that uses the narrowband TDD frame structure. Further, UE 806 maydelay an NPUSCH transmission 805 to an uplink subframe located in asecond radio frame that is subsequent to the first radio frame. In otherwords, interlacing is not enabled, and UE 806 may only monitor downlinksubframes or transmit using uplink subframes in a single radio frame,but not both.

Referring to FIG. 8B, UE 806 may receive information 801 indicating anarrowband TDD frame structure for narrowband communications from basestation 804. For example, the information 801 may indicate that thenarrowband TDD frame structure is one of configuration 0, 1, 2, 3, 4, 5,6, 1, or o from table 410 in FIG. 4.

In addition, UE 806 may receive a downlink grant 807 that allocates afirst set of subframes for the NPDCCH 809 and/or NPDSCH 809. Forexample, the downlink grant 807 may indicate that downlink subframes pto q are allocated for the NPDCCH 809 and/or NPDSCH 809. Further, UE 806may receive the NPDCCH 809 and/or NPDSCH 809 associated with thedownlink grant 807 in at least one subframe in the set of subframes p toq. In a first illustrative example, assume the narrowband TDD framestructure is configuration 1, and subframes 3, 4, and 5 (e.g., p isequal to 3 and q is equal to 5) are allocated in the downlink grant 807for the NPDCCH 809 and/or NPDSCH 809. In one aspect, the plurality ofsubframes may include one or more of uplink subframes, downlinksubframes, and special subframes.

In addition, UE 806 may receive an uplink grant 811 that allocates asecond set of subframes for the NPUCCH 813 and/or NPUSCH 813. Forexample, the second set of subframes may be located before the first setof subframes, located after the first set of subframes, and/or partiallyoverlap with the first set of subframes. In addition, UE 806 may berestricted to transmit the NPUCCH 813 and/or NPUSCH 813 using a subsetof subframes in the second set. In one aspect, the UE 806 may berestricted to a subset of subframes to accommodate switching fromreceiving the NPDCCH 809 and/or NPDSCH 809 to transmitting the NPUCCH813 and/or NPUSCH 813. In certain configurations, the downlink grant 807and the uplink grant 811 may be received in the same search space. Inone aspect, a NPUCCH (ACK) and a NPDSCH may not be interlaced.

Referring to the first illustrative example discussed above, assume theuplink grant 811 indicates that the UE 806 may transmit the NPUCCH 813and/or NPUSCH 813 in uplink subframes located in the set of subframes 1,2, 3, 4, 5, 6, 7, and 8. In addition, assume the UE 806 is restricted tosubframes that are located a number of subframes before the firstsubframe allocated for the NPDCCH 809 and/or NPDSCH 809 (e.g., subframep−a). In addition, assume UE 806 is restricted to subframes that arelocated b number of subframes after the last subframe allocated for theNPDCCH 809 and/or NPDSCH 809 (e.g., subframe q+b). Furthermore, assumethat a is equal to 1 and that b is equal to two. Hence in the firstillustrative example, UE 806 may transmit the NPUCCH 813 and/or NPUSCH813 using subframes 1, 2, and 8 because subframe 3 is restricted (e.g.,4−1=3) for switching and subframes 6 and 7 are also restricted (e.g.,5+2=7) for switching.

Alternatively, UE 806 may not use an entire subframe to switch fromuplink transmission to downlink monitoring. Therefore, the UE 806 may berestricted to transmit before or after the downlink subframes by acertain number of symbols rather than subframes. The restricted symbolsmay be punctured at the beginning or end of the restricted subframesdepending on whether NPDSCH and/or NPDCCH is being transmitted. Inscenarios when special subframes are included in the first set ofsubframes, the special subframe configuration may support switching timeand no additional switching time (e.g., symbols or subframes) may beused by UE 806.

Referring to FIG. 8C, UE 806 may receive information 801 indicating aTDD frame structure for narrowband communications from base station 804.For example, the information 801 may indicate that the narrowband TDDframe structure is one of configuration 0, 1, 2, 3, 4, 5, 6, 1, or ofrom table 410 in FIG. 4.

In addition, UE 806 may receive an uplink grant 815 that allocates afirst set of subframes for the NPUCCH 817 and/or NPUSCH 817. Forexample, the uplink grant 815 may indicate that downlink subframes p toq are allocated for the NPUCCH 817 and/or NPUSCH 817. Further, UE 806may transmit the NPUCCH 817 and/or NPUSCH 817 associated with the uplinkgrant 815 in at least one subframe in the set of subframes p to q. As anillustrative example, assume narrowband TDD frame structure isconfiguration 1, and subframes 6 and 7 (e.g., p is equal to 6 and q isequal to 7) are allocated in the uplink grant 815 for the NPUCCH 817and/or NPUSCH 817. In the illustrative example, the first set ofsubframes include a special subframe 6 and uplink subframe 7.

In addition, UE 806 may receive a downlink grant 819 that allocates asecond set of subframes for the NPDCCH 821 and/or NPDSCH 821, and UE 806may receive the NPDCCH 821 and/or NPDSCH 821 in the second set ofsubframes. In certain configurations, the second set of subframes may belocated before the first set of subframes, located after the first setof subframes, and/or partially overlap with the first set of subframes.In addition, UE 806 may be restricted to monitor a subset of subframesin the second set for the NPDCCH 821 and/or NPDSCH 821. In one aspect,the UE 806 may be restricted to monitor a set of the allocated downlinksubframes to accommodate switching from transmitting the NPUCCH 817and/or NPUSCH 817 to monitoring for the NPDCCH 821 and/or NPDSCH 821that may be received in the second set of subframes.

Referring to the illustrative example discussed above with respect toFIG. 8C, assume the downlink grant 819 indicates that the UE 806 thatdownlink subframes located between subframes 4, 5, 6, 7, 8, and 9 areallocated for the NPDCCH 821 and/or NPDSCH 821. In addition, assume theUE 806 is restricted to subframes that are located c number of subframesbefore the first subframe allocated for the NPUCCH 817 and/or NPUSCH 817(e.g., subframe p−c). In addition, assume UE 806 is restricted tosubframes that are located d number of subframes after the last subframeallocated for the NPUCCH 817 and/or NPUSCH 817 (e.g., subframe q+d).Furthermore, assume that c is equal to 1 and that d is equal to one.Hence in the illustrative example discussed with reference to FIG. 8C,UE 806 may monitor downlink subframes 4 and 9 and not subframe 5 becausesubframe 5 is restricted (e.g., 6−1=5) for switching. There are nodownlink subframes located after subframe 7, and thus no downlinksubframes after subframe 7 are restricted for switching.

Bitmap

FIG. 9 illustrates a data flow 900 that may be used for communicating abitmap associated with a narrowband TDD frame structure in accordancewith certain aspects of the disclosure. Base station 504 may correspondto, e.g., base station 102, 180, 604, 704, 804, 904, 1004, 1104, 2350,eNB 310, apparatus 1802/1802′, 2502/2502′. UE 506 may correspond to,e.g., UE 104, 350, 606, 706, 806, 906, 1006, 1106, 1850, 2550, apparatus2302/2302′. In addition, the base station 904 and the UE 906 may beconfigured to communicate using narrowband communications (e.g., NB-IoTand/or eMTC). For example, the UE 906 may be an NB-IoT device and/or aneMTC device.

In one aspect, base station 904 may determine 901 a narrowband TDD framestructure for narrowband communications that includes one or more of aset of downlink subframes, a set of uplink subframes, a set of specialsubframes, and/or a set of flexible subframes. For example, base station904 may determine 901 that the narrowband TDD frame structure is one ofconfiguration 0, 1, 2, 3, 4, 5, 6, 1, or o from table 410 in FIG. 4.

In another aspect, base station 904 may transmit a bitmap 903 associatedwith the narrowband TDD frame structure to UE 906. Bitmap 903 mayindicate the set of downlink subframes, the set of uplink subframes, theset of special subframes, and/or the set of flexible subframes in thedetermined narrowband TDD frame structure.

In one aspect, when base station 904 operates in in-band mode, a singlebitmap 903 indicating the set of downlink subframes, the set of uplinksubframes, the set of special subframes, and/or the set of flexiblesubframes may be transmitted to UE 906. Alternatively, when base station904 operates in standalone mode, a first bitmap 903 that indicates theset of downlink subframes, a second bitmap 903 that indicates the set ofuplink subframes, a third bitmap 903 that indicates the set of specialsubframes, and/or a fourth bitmap 903 that indicates the set of flexiblesubframes may be separately transmitted to UE 806.

In one configuration, a first length of the bitmap 903 associated withthe determined narrowband TDD frame structure may be longer than asecond length of a different bitmap associated with a narrowband FDDframe structure. For example, a single bitmap of length N (e.g., N=60)be used to indicate or more of downlink subframes and/or uplinksubframes in a narrowband FDD frame structure. In certainconfigurations, the length N of bitmap 903 used to indicate theavailable downlink subframes, uplink subframes, special subframes,and/or flexible subframes in the narrowband TDD frame structure may belarger (e.g., N=80) than the bitmap used to indicate the narrowband FDDframe structure. The length of the narrowband TDD frame structure bitmapmay be larger than the narrowband FDD frame structure bitmap becausethere may be more types of subframes available for allocation using anarrowband TDD frame structure as compared to a narrowband FDD framestructure.

When base station 904 allocates one or more flexible subframes for theNPDCCH and/or the NPDSCH, UE 906 may decode NRS and the NPDCCH and/orNPDSCH transmitted on the allocated flexible subframe(s). When basestation 904 allocates one or more flexible subframes for the NPUCCHand/or the NPUSCH, UE 906 may use the allocated flexible subframes totransmit the NPUCCH and/or the NPUSCH. When flexible subframes are notallocated for the NPDCCH, NPDSCH, NPUCCH, or NPUSCH, UE 906 may ignorethe flexible subframes. For example, the UE 906 may not perform NRSdetection on the flexible subframes when flexible subframes are notallocated for the NPDCCH, NPDSCH, NPUCCH, or NPUSCH.

Data Scrambling

Data scrambling may be used to transpose and/or invert signals orotherwise encode the NPDCCH and/or NPDSCH with a predeterminedscrambling sequence. The scrambling sequence may be unintelligible to aUE not equipped with an appropriately set descrambling device, and henceonly an intended UE may properly decode the NPDCCH and/or NPDSCH.

Using a narrowband FDD frame structure, the scrambling sequence for theNPDCCH and/or NPDSCH may remain the same for a predetermined number ofrepeated transmissions (e.g., at least four repeated transmissions)across a set of downlink subframes. To increase the chance of properlydecoding the NPDCCH and/or NPDSCH, a legacy UE may combine thescrambling sequence of the NPDCCH and/or NPDSCH across each of therepeated transmissions as long as the channel does not vary across therepeated transmissions. As an illustrative example, assume that thescrambling sequence for repeated transmissions of the NPDSCH using anarrowband FDD frame structure remains the same across four downlinksubframes. In addition, assume that the NPDSCH is repeated on subframes{5, 6, 8, 10, 13, 15, 16 17} across two radio frames that includesubframes 0-19. The scrambling sequence of the NPDSCH on subframes {5,6, 8, 10} may be based on the scrambling sequence associated withsubframe 5, and the scrambling sequence of the NPDSCH on subframes {13,14, 15, 17} may be based on the scrambling sequence associated withsubframe 13.

Using a narrowband TDD frame structure, uplink subframes and/or unusedflexible subframes may be located in between downlink subframes and/orspecial subframes used to transmit the NPDCCH and/or NPDSCH.Consequently, the duration over which repeated transmission of theNPDCCH and/or NPDSCH using a narrowband TDD frame structure may beincreased as compared to a duration of the same number of repetitionstransmitted using an FDD frame structure. The likelihood that channelconditions may change over the repeated transmissions using a narrowbandTDD frame structure may therefore be increased as compared to repeatedtransmissions using a narrowband FDD frame structure, and hence the UEmay be less likely to combine the repeated transmission.

There is a need for a technique that enables a UE to combine repeatedtransmissions that have the same scrambling sequence in a narrowband TDDframe structure.

FIG. 10 illustrates a data flow 100 that that may enable data scramblingof an NPDCCH and/or NPDSCH that is transmitted using a narrowband TDDframe structure in accordance with certain aspects of the disclosure.Base station 504 may correspond to, e.g., base station 102, 180, 604,704, 804, 904, 1004, 1104, 2350, eNB 310, apparatus 1802/1802′,2502/2502′. UE 506 may correspond to, e.g., UE 104, 350, 606, 706, 806,906, 1006, 1106, 1850, 2550, apparatus 2302/2302′. In addition, the basestation 1004 and the UE 1006 may be configured to communicate usingnarrowband communications (e.g., NB-IoT and/or eMTC). For example, theUE 1006 may be an NB-IoT device and/or an eMTC device.

In one aspect, base station 1004 may determine 1001 a narrowband TDDframe structure that includes one or more of a set of downlinksubframes, a set of uplink subframes, a set of special subframes, or aset of flexible subframes. For example, base station 1004 may determine1001 that the narrowband TDD frame structure is one of configuration 0,1, 2, 3, 4, 5, 6, 1, or o from table 410 in FIG. 4.

In addition, base station 1004 may group 1003 a plurality of subframesinto a plurality of subframe groups. In one aspect, each of theplurality of subframe groups may be associated with a particularscrambling sequence, and each subframe group may be determined based ona downlink subframe and a predetermined number of following subframes.

In a first example of FIG. 10, a scrambling sequence generator for theNPDCCH and/or NPDSCH at base station 1004 may be reinitialized afterevery min(RepetitionSize, M) absolute subframes. Absolute subframes maybe a predetermined M number of subframes that include all subframeswithin a range (e.g. four subframes) regardless of whether the subframesare used to transmit the NPDCCH and/or NPDSCH.

In a second example of FIG. 10, base station 1004 may use predefinedboundaries of subframes, and all NPDCCH and/or NPDSCH transmissions thatfall within a boundary may have the same scrambling based on the lowestsubframe index in that boundary. In one aspect, the boundaries may bedefined as mod(sub-frame-index−i_Delta, i_M)=0.

Further, base station 1004 may determine 1005 a first subframe group ofthe plurality of subframe groups associated with the first set ofsubframes and a second subframe group of the plurality of subframegroups associated with the second set of subframes. In both the firstexample and the second example of FIG. 10, assume M is equal to four,and that the NPDSCH is repeated on subframes {5, 6, 8, 10, 13, 14, 15,17} across two radio frames with subframes 0-19.

In the first example discussed above with respect to FIG. 10, the rangeof subframes (e.g., four subframes) starting with subframe 5 includessubframes 5, 6, 7, 8. The range of subframes (e.g., four subframes)starting with subframe 10 (e.g., the first subframe after the lastsubframe in the first group) includes subframes 10, 11, 12, 13. Further,the range of subframes (e.g., four subframes) starting with subframe 14(e.g., the first subframe after the last subframe in the second group)includes subframes 14, 15, 16, 17. Thus, base station 1004 may groupsubframes {5, 6, 8} into a first group, subframes {10, 13} into a secondgroup, and subframes {14, 15, 17} into a third group.

In a second example discussed above with respect to FIG. 10, theboundaries of the subframes would be {[0-3] [4-7] [8-11] [12-15] [16-19]}. Thus, base station 1004 may group subframes {0, 1, 2, 3} into a firstgroup, subframes {4, 5, 6, 7} into a second group, subframes {8, 9, 10,11} into a third group, subframes {12, 13, 14, 15} into a fourth group,and subframes {16, 17, 18, 19} into a fifth group.

Additionally, base station 1004 may determine 1007 a first scramblingsequence for the first set of downlink subframes in a first subframegroup and the second scrambling sequence for a second set of downlinksubframes in a second subframe group.

Referring to the first example discussed above with respect to FIG. 10,the scrambling sequence used by base station 1004 for the NPDSCHtransmitted in subframes {5, 6, 8} may be based on the scramblingsequence of subframe 5. In addition, scrambling sequence used by basestation 1004 for the NPDSCH transmitted in subframes {10, 13} may bebased on the scrambling sequence of subframe 10. Further, the scramblingsequence used by base station 1004 for the NPDSCH transmitted insubframes {14, 15, 17} may be based on subframe 14.

Referring to the second example discussed above with respect to FIG. 10,the scrambling sequence used by base station 1004 for the NPDSCHtransmitted in subframes {5, 6} may be based on subframe 4, thescrambling sequence used by base station 1004 for the NPDSCH transmittedin subframes {8, 10} may be based on subframe 8, the scrambling sequenceused by base station 1004 for the NPDSCH transmitted in subframes {13,14, 15} may be based on subframe 12, and the scrambling sequence used bybase station 1004 for the NPDSCH transmitted in subframe {17} may bebased on subframe 16.

Base station 1004 may transmit 1009 a series of repetitions of theNPDCCH and/or NPDSCH based on either the first example or the secondexample described above with respect to FIG. 10.

Redundancy Version and Cycling Pattern

Different redundancy versions of the NPDCCH and/or NPDSCH may betransmitted using a cycling pattern in addition to or instead of thedata scrambling sequences discussed above with respect to FIG. 10.Because a narrowband TDD frame structure may not include a large numberof contiguous downlink subframes, a UE may not be able to combine theredundancy versions if channel conditions change over one or morerepetition cycles. Thus, there is a need for a redundancy versioncycling pattern that may increase the chance of a UE properly combiningredundancy versions transmitted by a base station using a narrowband TDDframe structure.

FIG. 11 illustrates a data flow 1100 that may enable a redundancyversion cycling pattern used for an NPDCCH and/or NPDSCH in accordancewith certain aspects of the disclosure. Base station 504 may correspondto, e.g., base station 102, 180, 604, 704, 804, 904, 1004, 1104, 2350,eNB 310, apparatus 1802/1802′, 2502/2502′. UE 506 may correspond to,e.g., UE 104, 350, 606, 706, 806, 906, 1006, 1106, 1850, 2550, apparatus2302/2302′. In addition, the base station 1104 and the UE 1106 may beconfigured to communicate using narrowband communications (e.g., NB-IoTand/or eMTC). For example, the UE 1106 may be an NB-IoT device and/or aneMTC device.

In one aspect, base station 1104 may determine 1101 a narrowband TDDframe structure that includes one or more of a set of downlinksubframes, a set of uplink subframes, a set of special subframes, or aset of flexible subframes. For example, base station 1104 may determine1101 that the narrowband TDD frame structure is one of configuration 0,1, 2, 3, 4, 5, 6, 1, or o from table 410 in FIG. 4.

In addition, base station 1104 may transmit a first redundancy version(RV0) of the NPDCCH 1103 and/or NPDSCH 1103 and a second redundancyversion (RV1) 1105 of the NPDCCH 1105 and/or NPDSCH 1105 using thenarrowband TDD frame structure. In one aspect, a number of repetitionsof RV0 may be transmitted in a repetition cycle before switching to RV1,and vice versa. The number of repetitions in a repetition cycle may bebased on a number of contiguous downlink subframes in the determinednarrowband TDD frame structure and a predetermined maximum number ofrepetitions.

As an illustrative example, assume configuration 1 is used for thenarrowband TDD frame structure, that sixteen repetitions of the NPDCCH1103 and/or NPDSCH 1103 are configured, that two versions of repetitionare configured, and that the maximum number of repetitions in arepetition cycle is two. Hence in the illustrative example, the sequencetransmitted by base station 1104 is {RV0RV0 RV1RV1 RV0RV0 RV RV0RV0 RVRV0RV0 RV RV0RV0 RV RV0RV0 RV RV0RV0 RV RV0RV0 RV}.

FIGS. 12A-12C are a flowchart 1200 of a method of wirelesscommunication. The method may be performed by a base station (e.g., thebase station 102, 180, 504, 604, 704, 804, 904, 1004, 1104, 2350, eNB310, the apparatus 1802/1802′). In FIGS. 12A-12C, operations with dashedlines indicate optional operations.

In FIG. 12A, at 1202, the base station may determine to transmit aphysical downlink channel in a subframe in a narrowband TDD framestructure of a plurality of narrowband TDD frame structures fornarrowband communications. In one aspect, the physical downlink channelmay include at least one of a NPDSCH or a NPDCCH. For example, referringto FIG. 5, base station 504 may determine 501 to transmit an NPDCCHand/or NPDSCH in a subframe in a narrowband TDD frame structure. Forexample, the base station 504 may determine 501 the narrowband TDD framestructure is one of configuration 0, 1, 2, 3, 4, 5, 6, 1, or o fromtable 410 in FIG. 4.

In FIG. 12A, at 1204, the base station may determine whether thesubframe is a special subframe or a downlink subframe when thenarrowband TDD frame structure includes one or more special subframes.For example, referring to FIG. 5, base station 504 may determine 503whether a subframe allocated for an NPDCCH and/or NPDSCH is a specialsubframe or a downlink subframe when the determined narrowband TDD framestructure includes one or more special subframes (e.g., configurations0, 1, 2, 3, 4, 5, 6, and n in FIG. 4).

In FIG. 12A, at 1206, the base station may determine how to transmit anarrowband physical downlink channel based on the determination whetherthe subframe is a special subframe or a downlink subframe. For example,referring to FIG. 5, base station 504 may determine 505 how to transmitthe NPDCCH and/or NPDSCH and allocate resources in one or more downlinksubframe and/or special subframes. In one aspect, the base station 504may allocate resources for the NPDCCH and/or NPDSCH in all availabledownlink subframes (e.g., downlink subframes not being used forswitching). However, the allocation of resources on a special subframeby base station 504 may be a function of a special subframeconfiguration (e.g., how many resources are available in the DwPTSportion) and/or the determined narrowband TDD frame.

In FIG. 12A, at 1208, the base station may determine how to transmit anarrowband physical downlink channel based on the determination whetherthe subframe is a special subframe or a downlink subframe by determiningto transmit the narrowband physical downlink channel in the subframewhen the subframe is a downlink subframe. For example, referring to FIG.5, the base station 504 may allocate resources for the NPDCCH and/orNPDSCH in all available downlink subframes (e.g., downlink subframes notbeing used for switching).

In FIG. 12A, at 1210, the base station may determine how to transmit anarrowband physical downlink channel based on the determination whetherthe subframe is a special subframe or a downlink subframe by determiningto refrain from transmitting the narrowband physical downlink channel inthe subframe when the subframe is a special subframe. For example,referring to FIG. 5, in a first configuration, base station 504 maydetermine 505 to transmit the NPDCCH and/or NPDSCH in downlink subframesand not special subframes. In the first configuration, base station 504may not allocate resources for the NPDCCH and/or NPDSCH on specialsubframes.

In FIG. 12A, at 1212, the base station may determine how to transmit anarrowband physical downlink channel based on the determination whetherthe subframe is a special subframe or a downlink subframe by determiningto transmit the narrowband physical downlink channel in the subframewith a subset of OFDM symbols in the special subframe punctured when thesubframe is a special subframe. In an aspect, the narrowband physicaldownlink channel may be transmitted. For example, referring to FIG. 5,in a second configuration, base station 504 may determine 505 totransmit the NPDCCH 509 and/or NPDSCH 509 in special subframes as wellas downlink subframes. In the second configuration, the base station 504may allocate resources for the NPDCCH and/or NPDSCH in downlinksubframes as well as the DwPTS portion of one or more special subframes.In a first aspect of the second configuration, base station 504 maypuncture the OFDM symbols in the UpPTS portion of the one or morespecial subframes.

In FIG. 12A, at 1214, the base station may determine how to transmit anarrowband physical downlink channel based on the determination whetherthe subframe is a special subframe or a downlink subframe by determiningto transmit the narrowband physical downlink channel in the subframewith at least OFDM symbols in the downlink portion of the specialsubframe punctured when the subframe is a special subframe. For example,referring to FIG. 5, in a second aspect of the second configuration,base station 504 may puncture the OFDM symbols in the DwPTS portion andthe UpPTS portion of the one or more special subframes. By puncturingthe OFDM symbols in the DwPTS portion and the UpPTS portion of the oneor more special subframes, UE 506 may ignore (e.g., not monitor ordiscard) the special subframes while receiving NPDCCH and/or NPDSCH in aradio frame.

In FIG. 12B, at 1216, the base station may determine how to transmit anarrowband physical downlink channel based on the determination whetherthe subframe is a special subframe or a downlink subframe by determiningto transmit the narrowband physical downlink channel in the subframewhen the subframe is a special subframe and a number of OFDM symbols inthe special subframe is greater than a predetermined threshold. Forexample, referring to FIG. 5, in a third configuration, base station 504may determine 505 to transmit the NPDCCH 509 and/or NPDSCH 509 in aspecial subframe when a number of OFDM symbols in the special subframeis greater than a predetermined threshold. Otherwise, base station 504may transmit a repetition of the NPDCCH 511 and/or NPDCCH 511 in thenext downlink subframe. As an illustrative example, assume configuration2 is used for the narrowband TDD frame structure, that special subframe1 has ten OFDM symbols, and that the predetermined threshold is fiveOFDM symbols. Here, base station 504 may transmit the NPDCCH 509 and/orNPDSCH 509 in subframe 0 and a repetition of the NPDCCH 511 and/orNPDSCH 511 in special subframe 1.

In FIG. 12B, at 1218, the base station may determine how to transmit anarrowband physical downlink channel based on the determination whetherthe subframe is a special subframe or a downlink subframe by determiningto transmit the narrowband physical downlink channel in the subframewith a subset of OFDM symbols punctured in the special subframe when thesubframe is a special subframe and a number of OFDM symbols in thespecial subframe is less than a predetermined threshold. For example,referring to FIG. 5, base station 504 may determine 505 to transmit theNPDCCH 509 and/or NPDSCH 509 in the special subframe when a number ofOFDM symbols in the special subframe is less than a predeterminedthreshold. In the fourth configuration, base station 504 may transmitthe NPDCCH 509 and/or NPDSCH 509 with a subset of OFDM symbols (e.g., asubset of the OFDM symbols in the DwPTS portion and/or the UpPTSportion) punctured in the special subframe. As an illustrative example,assume configuration 2 is used for the narrowband TDD frame structure,that special subframe 1 has five OFDM symbols, and that thepredetermined threshold is ten OFDM symbols. Here, base station 504 maytransmit the NPDCCH 509 and/or NPDSCH 509 in subframe 0 and transmit arepetition of the NPDCCH 511 and/or NPDSCH 511 in special subframe 1with a subset of the OFDM symbols in special subframe 1 punctured.

In FIG. 12B, at 1220, the base station may determine how to transmit anarrowband physical downlink channel based on the determination whetherthe subframe is a special subframe or a downlink subframe by determiningto refrain from transmitting the narrowband physical downlink channel inthe subframe when the subframe is a special subframe and a number ofOFDM symbols in the special subframe is less than a predeterminedthreshold. For example, referring to FIG. 5, in a fifth configuration,base station 504 may determine 505 to refrain from transmitting theNPDCCH and/or NPDSCH in a special subframe when a number of OFDM symbolsin the special subframe is less than a predetermined threshold. In thefifth configuration, base station 504 may transmit the NPDCCH 511 and/orNPDSCH 511 in the next available downlink subframe. As an illustrativeexample, assume configuration 2 is used for the narrowband TDD framestructure, that special subframe 1 has five OFDM symbols, and that thepredetermined threshold is ten OFDM symbols. Here, base station 504 maytransmit the NPDCCH 509 and/or NPDSCH 509 in subframe 0 and wait untilthe next downlink subframe 3 to transmit a repetition of the NPDCCH 511and/or NPDSCH 511.

In FIG. 12B, at 1222, the base station may determine how to transmit anarrowband physical downlink channel based on the determination whetherthe subframe is a special subframe or a downlink subframe by determiningto drop the transmission of the narrowband physical downlink channel inthe subframe when the subframe is a special subframe and a number ofOFDM symbols in the special subframe is less than a predeterminedthreshold. For example, referring to FIG. 5, base station 504 maydetermine 505 to drop the transmission of the NPDCCH and/or NPDSCH in aspecial subframe when a number of OFDM symbols in the special subframeis less than a predetermined threshold.

In FIG. 12C, at 1224, the base station may rate match the narrowbandphysical downlink channel in the subframe based on the number ofdownlink of OFDM symbols in the subframe. For example, referring to FIG.5, base station 504 may rate match the NPDCCH and/or NPDSCH in thesubframe (e.g., downlink subframe or special subframe) based on thenumber of downlink OFDM symbols in the subframe. A special subframe mayhave a fewer number of OFDM symbols than a downlink subframe becauseonly the DwPTS portion of the special subframe is dedicated for anNPDCCH and/or NPDSCH. Hence, the rate matching for a special subframemay be different than the rate matching for a downlink subframe.

In FIG. 12C, at 1226, the base station may transmit the narrowbandphysical downlink channel. For example, referring to FIG. 5, whenconfiguration 2 is used as the narrowband TDD frame structure, the basestation 504 may transmit the NPDCCH 507 and/or NPDSCH 507 in subframe 0,and a repetition of the NPDCCH 511 and/or NPDSCH 511 may be transmittedin subframe 3 (e.g., the next downlink subframe in configuration 2). Inanother configuration, base station 504 may determine 505 to transmitthe NPDCCH 509 and/or NPDSCH 509 in special subframes and to transmitthe NPDCCH 507 and/or NPDSCH 507 in downlink subframes.

In FIG. 12C, at 1228, the base station may transmit the narrowbandphysical downlink channel in a subsequent downlink subframe. Forexample, referring to FIG. 5, when configuration 2 is used as thenarrowband TDD frame structure, the base station 504 may transmit theNPDCCH 507 and/or NPDSCH 507 in subframe 0, and a repetition of theNPDCCH 511 and/or NPDSCH 511 may be transmitted in subframe 3 (e.g., thenext downlink subframe in configuration 2).

In FIG. 12C, at 1230, the base station may transmit the narrowbandphysical downlink channel in a next downlink subframe upon determiningto refrain from transmitting the narrowband physical downlink channel inthe subframe. For example, referring to FIG. 5, when configuration 2 isused as the narrowband TDD frame structure, the base station 504 maytransmit the NPDCCH 507 and/or NPDSCH 507 in subframe 0, and arepetition of the NPDCCH 511 and/or NPDSCH 511 may be transmitted insubframe 3 (e.g., the next downlink subframe in configuration 2).

FIGS. 13A-13C are a flowchart 1300 of a method of wirelesscommunication. The method may be performed by a base station (e.g., thebase station 102, 180, 504, 604, 704, 804, 904, 1004, 1104, 2350, 2550,2750, eNB 310, the apparatus 1802/1802′). In FIG. 13, operations withdashed lines indicate optional operations.

In FIG. 13A, at 1302, the base station may determine a narrowband TDDframe structure of a group of narrowband TDD frame structures fornarrowband communications. For example, referring to FIGS. 6A and 6B,base station 604 may determine 601 a narrowband TDD frame structure(e.g., configuration 0, 1, 2, 3, 4, 5, 6, l, or o listed in table 410 inFIG. 4.) is used for narrowband communications with UE 606.

In FIG. 13A, at 1304, the base station may allocate at least one RB inthe narrowband TDD frame structure for transmitting a narrowbandphysical downlink channel to a first UE. For example, referring to FIGS.6A and 6B, base station 604 may allocate 603 at least one RB in thenarrowband TDD frame structure for transmitting an NPDCCH and/or NPDSCHto UE 606.

In FIG. 13A, at 1306, the base station may allocate at least one RB inthe narrowband TDD frame structure for transmitting a narrowbandphysical downlink channel to a first UE by allocating the at least oneRB in the narrowband TDD frame structure for transmitting the narrowbandphysical downlink channel to a second UE. In one aspect, a modifiedlegacy pilot structure may be used to map the narrowband physicaldownlink channel to the UE-RS. In another aspect, the NRS and the UE-RSmay not share resources in the modified legacy pilot structure. In afurther aspect, a legacy pilot signal structure may be used to map thedownlink channel to the UE-RS. In still another aspect, the NRS and theUE-RS may not share resources in the legacy pilot structure. Forexample, referring to FIGS. 6A and 6B, if multi-user MIMO capability issupported (e.g. if two UEs are allocated by base station 604 to the sameRB for NPDCCH and/or NPDSCH), the legacy port 107/108 pilot structure orlegacy port 109/110 pilot structure may be reused. In one aspect, theUE-RS 607 may not share resources with the NRS 613 in the legacy pilotstructure.

In FIG. 13A, at 1308, the base station may map a UE-RS to the at leastone RB allocated for transmitting the narrowband physical downlinkchannel. For example, referring to FIGS. 6A and 6B, base station 604 maymap 605 a UE-RS to the at least one RB allocated for the NPDCCH and/orNPDSCH. In one aspect, base station 604 may use a legacy pilot structure(e.g., legacy port 5 pilot structure, modified legacy port 107/108 pilotstructure, modified legacy port 109/110 pilot structure, etc.) topopulate the UE-RS 607.

In FIG. 13A, at 1310, the base station may determine at least onedownlink subframe in the narrowband TDD frame structure that includesthe narrowband physical downlink channel and that does not include theNRS. For example, referring to FIGS. 6A and 6B, the UE-RS 607 may notshare resources with a NRS 613 in the legacy pilot structure.

In FIG. 13B, at 1312, the base station may transmit the UE-RS to thefirst UE based on the mapping. For example, referring to FIGS. 6A and6B, base station 604 may transmit the UE-RS 607 to the UE 606 based onthe mapping. In one aspect, base station 604 may use a legacy pilotstructure (e.g., legacy port 5 pilot structure, modified legacy port107/108 pilot structure, modified legacy port 109/110 pilot structure,etc.) to populate the UE-RS 607.

In FIG. 13B, at 1314, the base station may transmit the UE-RS in RElocations associated with NRS transmissions when it is determined thatthe narrowband physical downlink channel is transmitted in the at leastone downlink subframe that does not include the NRS. For example,referring to FIGS. 6A and 6B, the network (e.g., higher layers) mayindicate certain downlink subframes that do not include NRS 613. If theNPDCCH and/or NPDSCH is transmitted in subframes that do not include NRS613, base station 604 may transmit UE-RS 607 in the same REs as the NRS613.

In FIG. 13B, at 1316, the base station may receive a first channelestimate associated with the UE-RS from the first UE. In one aspect, thefirst channel estimate may be received in the TDD frame structureselected for narrowband communications. For example, referring to FIGS.6A and 6B, base station 604 may receive a first channel estimate 609associated with the UE-RS (e.g., the channel used to transmit the UE-RS607) transmitted from the UE 606.

In FIG. 13B, at 1318, the base station may perform a beamformingprocedure using the first channel estimate received from the first UE.For example, referring to FIGS. 6A and 6B, base station 604 may perform611 a beamforming procedure using the first channel estimate 609received from the UE 606.

In FIG. 13B, at 1320, the base station may transmit a NRS to the firstUE using the narrowband TDD frame structure selected for the narrowbandcommunications. For example, referring to FIGS. 6A and 6B, base station604 may transmit an NRS 613 to UE 606.

In FIG. 13C, at 1322, the base station may receive a second channelestimate associated with the NRS from the first UE. In one aspect, thesecond channel estimate may be received in the TDD frame structureselected for narrowband communications. For example, referring to FIGS.6A and 6B, base station 604 may receive a second channel estimate 615associated with the NRS 613 from UE 606.

In FIG. 13C, at 1324, the base station may determine a precoding foreach of a plurality of transmit antennas used to transmit the downlinkchannel based on the second channel estimate. In one aspect, theprecoding is constant across a predetermined number of subframes. Inanother aspect, the precoding is applied to a narrowband carrierspecific to the first UE. In a further aspect, the narrowband carrier isa non-anchor carrier. For example, referring to FIGS. 6A and 6B, basestation 604 may use the second channel estimate to determine 617 aprecoding for each of a plurality of transmit antennas used to transmitthe NPDCCH and/or NPDSCH.

In FIG. 13C, at 1326, the base station may signal to the first UE thatmultiple transmit antennas at the base station transmit the NRS and thateach of the multiple transmit antennas are associated with a sameprecoding. In one aspect, the signaling may include DCI or RRCinformation. For example, referring to FIGS. 6A and 6B, base station 604may signal 619 that each of the multiple transmit antennas areassociated with the same precoding. In certain configurations, thesignal 619 may indicate that the NRS 613 uses the same precoding for apredetermined number of radio frames (e.g., ten 10 radio frames) beforeswitching to another precoding. In one aspect, the signal 619 may besent as DCI or RRC messaging. In one configuration, the signal 619 mayindicate that the NPDCCH is transmitted using a first number of antennas(e.g., one, two, three, etc.) and the NPDSCH is transmitted from asecond number of antennas (e.g., one, two, three, etc.).

In FIG. 13C, at 1328, the base station may transmit the narrowbandphysical downlink channel transmission to the UE based on thebeamforming procedure. For example, referring to FIGS. 6A and 6B, theNPDCCH 621 and/or NPDSCH 621 may be transmitted by base station 604using a data stream from each of the transmit antennas based on thebeamforming and/or precoding. The precoding may be applied to anarrowband carrier (e.g., non-anchor carrier) specific to UE 606.

In FIG. 13C, at 1330, the base station may transmit the narrowbandphysical downlink channel transmission to the UE based on thebeamforming procedure by transmitting a data stream associated with thenarrowband physical downlink channel from each of the plurality oftransmit antennas based on the precoding. For example, referring toFIGS. 6A and 6B, the NPDCCH 621 and/or NPDSCH 621 may be transmitted bybase station 604 using a data stream from each of the transmit antennasbased on the beamforming and/or precoding. The precoding may be appliedto a narrowband carrier (e.g., non-anchor carrier) specific to UE 606.

FIGS. 14A and 14B are a flowchart 1400 of a method of wirelesscommunication. The method may be performed by a base station (e.g., thebase station 102, 180, 504, 604, 704, 804, 904, 1004, 1104, 2350, 2550,2750, eNB 310, the apparatus 1802/1802′). In FIG. 14, operations withdashed lines indicate optional operations.

In FIG. 14A, at 1402, the base station may determine a narrowband TDDframe structure of a group of narrowband TDD frame structures fornarrowband communications. For example, referring to FIGS. 7A and 7B,base station 704 may determine 701 to transmit an NPDCCH and/or NPDSCHusing a subframe in a narrowband TDD frame structure. For example, thebase station 704 may determine 701 the narrowband TDD frame structure isone of configuration 0, 1, 2, 3, 4, 5, 6, 1, or o from table 410 in FIG.4.

In FIG. 14A, at 1404, the base station may determine a first set ofsubframes in the narrowband TDD frame structure used for transmitting adownlink control channel to a UE. In one aspect, a last subframe in thefirst set of subframes may be subframe n. For example, referring toFIGS. 7A and 7B, base station 704 may determine 703 a first set ofsubframes in the narrowband TDD frame structure used to transmit theNPDCCH to UE 706. For example, a last subframe in the first set ofsubframes may be subframe n. In one example, assume that configuration 2(e.g., see table 410 in FIG. 4) is used as the narrowband TDD framestructure. In addition, assume that the first set of subframes used totransmit the NPDCCH includes subframes 0 and 1 (e.g., n is equal to 1).

In FIG. 14A, at 1406, the base station may schedule a first uplinksubframe in the narrowband TDD frame structure used by the UE forreporting a first ACK/NACK associated with the downlink control channel.In one aspect, the first uplink subframe may be delayed based on k₀number of subframes after the subframe n. For example, referring toFIGS. 7A and 7B, base station 704 may schedule 705 a first uplinksubframe in the narrowband TDD frame structure for the UE 706 to reporta first ACK/NACK associated with the NPDCCH. In one configuration, thefirst uplink subframe may be delayed based on k₀ number of subframesafter the subframe n. In other words, UE 706 may transmit the firstACK/NACK in subframe n+k₀. In one example associated with FIG. 7, assumethat configuration 2 (e.g., see table 410 in FIG. 4) is used as thenarrowband TDD frame structure. In addition, assume that the first setof subframes used to transmit the NPDCCH includes subframes 0 and 1(e.g., n is equal to 1), and that k₀ is equal to 1. Hence, the firstACK/NACK associated with the NPDCCH may be transmitted by UE 706 insubframe 2 (e.g., 1+1=2) of the narrowband TDD frame structure.

In FIG. 14A, at 1408, the base station may signal information associatedwith the k₀ number of subframes to the UE in a first delay field in aDCI transmission. For example, referring to FIGS. 7A and 7B, information707 associated with the k₀ number of subframes may be signaled to UE 706in a first delay field in a DCI transmission.

In FIG. 14A, at 1410, the base station may determine a second set ofsubframes in the narrowband TDD frame structure used for transmitting adownlink data channel to the UE. In one aspect, a first subframe in thesecond set of subframes may be subframe n+k₀+x. In another aspect, alast subframe in the second set of subframes may be subframe n+k₀+x+y.In a further aspect, both x and y may be positive integers. For example,referring to FIGS. 7A and 7B, base station 704 may determine 709 asecond set of subframes in the narrowband TDD frame structure used totransmit the NPDSCH to UE 706. In one aspect, a first subframe in thesecond set of subframes may be located x number of subframes after thesubframe allocated for the first ACK/NACK transmission. For example, thefirst subframe in the second set of subframes is subframe n+k₀+x. A lastsubframe in the second set of subframes may be y subframes after thefirst subframe in the second set. For example, the last subframe in thesecond set of subframes may be subframe n+k₀+x+y. Both x and y may bepositive integers. Referring again to the example discussed above withrespect to FIG. 7, further assume that the second set of subframes aresubframes 3, 4, and 5 in configuration 2. In the example, x is equal to1 and y is equal to 2.

In FIG. 14B, at 1412, the base station may schedule a second uplinksubframe in the narrowband TDD frame structure used by the UE forreporting a second ACK/NACK associated with the downlink data channel.In one aspect, the second uplink subframe may be delayed m₀ number ofsubframes after the subframe n+k₀+x+y. In another aspect, the m₀ numberof subframes may include at least one of a number of downlink subframesor a number of uplink subframes. For example, referring to FIGS. 7A and7B, base station 704 may schedule 711 a second uplink subframe in thenarrowband TDD frame structure for the UE 706 to report a secondACK/NACK associated with the NPDSCH. In one aspect, the second uplinksubframe may be delayed m₀ number of subframes after the last subframeused to transmit the NPDSCH (e.g., subframe n+k₀+x+y), and the m₀ numberof subframes may include at least one of a number of downlink subframesand/or a number of uplink subframes. Referring again to the examplediscussed above with respect to FIG. 7, further assume that the secondset of subframes are subframes 3, 4, and 5 in configuration 2. In theexample, x is equal to 1 and y is equal to 2. In a first scenario,assume m₀ is equal to 3 when only downlink subframes are included in thedelayed number of subframes. In a second scenario, assume m₀ is equal to4 when downlink subframes and uplink subframes are included in thedelayed number of subframes. In either scenario, the second ACK/NACKassociated with the NPDSCH may be transmitted by UE 706 in subframe 2 inthe next radio frame after the radio frame in which the NPDSCH isreceived by UE 706. Additionally and/or alternatively, m₀ may onlyinclude valid uplink subframes and/or downlink subframes (e.g.,subframes available for transmission and not switching).

In FIG. 14B, at 1414, the base station may signal information associatedwith the m₀ number of subframes to the UE in a second delay field in theDCI transmission. For example, referring to FIGS. 7A and 7B, information713 associated with the m₀ number of subframes may be signaled to UE 706in a second delay field in the DCI transmission. In one configuration,the information 707, 713 may be signaled in the same DCI transmission.In another configuration, the information 707, 713 may be signaled indifferent DCI transmissions.

In FIG. 14B, at 1416, the base station may receive a bundle including aplurality of ACK/NACKs from the UE. In one aspect, each ACK/NACK in thebundle may be associated with a different HARQ process. For example,referring to FIGS. 7A and 7B, base station 704 may receive a bundle 715including a plurality of ACK/NACKs from UE 706. In one aspect, eachACK/NACK in the bundle may be associated with a different HARQ processassociated with one or more NPDCCH transmissions and/or NPDSCHtransmissions.

FIG. 15 is a flowchart 1500 of a method of wireless communication. Themethod may be performed by a base station (e.g., the base station 102,180, 504, 604, 704, 804, 904, 1004, 1104, 2350, 2550, 2750, eNB 310, theapparatus 1802/1802′). In FIG. 15, operations with dashed lines indicateoptional operations.

At 1502, the base station may determine a narrowband time TDD framestructure for narrowband communications. In one aspect, the narrowbandTDD frame structure may include one or more of a set of downlinksubframes, a set of uplink subframes, a set of special subframes, or aset of flexible subframes. In one aspect, a flexible subframe may beconfigurable by the base station as either a downlink subframe or anuplink subframe. For example, referring to FIG. 9, base station 904 maydetermine 901 a narrowband TDD frame structure for narrowbandcommunications that includes one or more of a set of downlink subframes,a set of uplink subframes, a set of special subframes, and/or a set offlexible subframes. For example, base station 904 may determine 901 thatthe narrowband TDD frame structure is one of configuration 0, 1, 2, 3,4, 5, 6, 1, or o from table 410 in FIG. 4.

At 1504, the base station may transmit a bitmap associated with thenarrowband TDD frame structure to a UE. In one aspect, the bitmap mayindicate the one or more of the set of downlink subframes, the set ofuplink subframes, the set of special subframes, or the set of flexiblesubframes. In another aspect, a first length of the bitmap associatedwith the narrowband TDD frame structure may be longer than a secondlength of a different bitmap associated with a narrowband FDD framestructure. For example, referring to FIG. 9, base station 904 maytransmit a bitmap 903 associated with the narrowband TDD frame structureto UE 906. Bitmap 903 may indicate the set of downlink subframes, theset of uplink subframes, the set of special subframes, and/or the set offlexible subframes in the determined narrowband TDD frame structure.

At 1506, the base station may transmit a bitmap associated with thenarrowband TDD frame structure to a UE by transmitting a single bitmapindicating the one or more of the set of downlink subframes, the set ofuplink subframes, the set of special subframes, or the set of flexiblesubframes. For example, referring to FIG. 9, when base station 904 isoperating in in-band mode, a single bitmap 903 indicating the set ofdownlink subframes, the set of uplink subframes, the set of specialsubframes, and/or the set of flexible subframes may be transmitted to UE906.

At 1508, the base station may transmit a bitmap associated with thenarrowband TDD frame structure to a UE by transmitting first informationindicating the set of downlink subframes. For example, referring to FIG.9, when base station 904 is operating in standalone mode, a first bitmap903 that indicates the set of downlink subframes may be separatelytransmitted to UE 806.

At 1510, the base station may transmit a bitmap associated with thenarrowband TDD frame structure to a UE by transmitting secondinformation indicating the set of uplink subframes. For example,referring to FIG. 9, when base station 904 is operating in standalonemode, a second bitmap 903 that indicates the set of uplink subframes maybe separately transmitted to UE 806.

At 1512, the base station may transmit a bitmap associated with thenarrowband TDD frame structure to a UE by transmitting third informationindicating the set of special subframes. For example, referring to FIG.9, when base station 904 is operating in standalone mode, a third bitmap903 that indicates the set of special subframes may be separatelytransmitted to UE 806.

At 1514, the base station may transmit a bitmap associated with thenarrowband TDD frame structure to a UE by transmitting fourthinformation indicating the set of flexible subframes. For example,referring to FIG. 9, when base station 904 is operating in standalonemode, a fourth bitmap 903 that indicates the set of flexible subframesmay be separately transmitted to UE 806.

FIG. 16 is a flowchart 1600 of a method of wireless communication. Themethod may be performed by a base station (e.g., the base station 102,180, 504, 604, 704, 804, 904, 1004, 1104, 2350, 2550, 2750, eNB 310, theapparatus 1802/1802′). In FIG. 16, operations with dashed lines indicateoptional operations.

At 1602, the base station may determine a narrowband TDD frame structureof a group of narrowband TDD frame structures for narrowbandcommunications. For example, referring to FIG. 10, base station 1004 maydetermine 1001 a narrowband TDD frame structure that includes one ormore of a set of downlink subframes, a set of uplink subframes, a set ofspecial subframes, or a set of flexible subframes. For example, basestation 1004 may determine 1001 that the narrowband TDD frame structureis one of configuration 0, 1, 2, 3, 4, 5, 6, 1, or o from table 410 inFIG. 4.

At 1604, the base station may group a plurality of subframes into aplurality of subframe groups. In one aspect, each of the plurality ofsubframe groups may be associated with a particular scrambling sequence.In another aspect, each subframe group may be determined based on adownlink subframe and a predetermined number of following subframes. Ina further aspect, none of the subframe groups may have overlappingsubframes. For example, referring to FIG. 10, base station 1004 maygroup 1003 a plurality of subframes into a plurality of subframe groups.In one aspect, each of the plurality of subframe groups may beassociated with a particular scrambling sequence, and each subframegroup may be determined based on a downlink subframe and a predeterminednumber of following subframes. In a first example of FIG. 10, ascrambling sequence generator for the NPDCCH and/or NPDSCH at basestation 1004 may be reinitialized after every min(RepetitionSize, M)absolute subframes. Absolute subframes may be a predetermined number ofsubframes that include all subframes within a range (e.g. foursubframes) regardless of whether the subframes are used to transmit theNPDCCH and/or NPDSCH. In a second example of FIG. 10, base station 1004may use predefined boundaries of subframes and all NPDCCH and/or NPDSCHtransmissions that fall within a boundary may have the same scramblingbased on the lowest subframe index in that boundary. In one aspect, theboundaries may be defined as mod(sub-frame-index−i_Delta, i_M)=0.

At 1606, the base station may determine a first subframe group of theplurality of subframe groups associated with the first set of subframesand a second subframe group of the plurality of subframe groupsassociated with the second set of subframes. For example, referring toFIG. 10, base station 1004 may determine 1005 a first subframe group ofthe plurality of subframe groups associated with the first set ofsubframes and a second subframe group of the plurality of subframegroups associated with the second set of subframes. In both the firstexample and the second example of FIG. 10, assume M is equal to four,and that the NPDSCH is repeated on subframes {5, 6, 8, 10, 13, 14, 15,17} across two radio frames with subframes 0-19. In the first examplediscussed above with respect to FIG. 10, the range of subframes (e.g.,four subframes) starting with subframe 5 includes subframes 5, 6, 7, 8.The range of subframes (e.g., four subframes) starting with subframe 10(e.g., the first subframe after the last subframe in the first group)includes subframes 10, 11, 12, 13. Further, the range of subframes(e.g., four subframes) starting with subframe 14 (e.g., the firstsubframe after the last subframe in the second group) includes subframes14, 15, 16, 17. Thus, base station 1004 may group subframes {5, 6, 8}into a first group, subframes {10, 13} into a second group, andsubframes {14, 15, 17} into a third group. In the second examplediscussed above with respect to FIG. 10, the boundaries of the subframeswould be {[0-3] [4-7] [8-11] [12-15] [16-19] }. Thus, base station 1004may group subframes {0, 1, 2, 3} into a first group, subframes {4, 5, 6,7} into a second group, subframes {8, 9, 10, 11} into a third group,subframes {12, 13, 14, 15} into a fourth group, and subframes {16, 17,18, 19} into a fifth group.

At 1608, the base station may determine a first scrambling sequence forthe first set of downlink subframes in a first subframe group and thesecond scrambling sequence for a second set of downlink subframes in asecond subframe group. In one aspect, the first set of downlinksubframes may include a different number of subframes than the secondset of downlink subframes. For example, referring to FIG. 10, basestation 1004 may determine 1007 a first scrambling sequence for thefirst set of downlink subframes in a first subframe group and the secondscrambling sequence for a second set of downlink subframes in a secondsubframe group. Referring to the first example discussed above withrespect to FIG. 10, the scrambling sequence used by base station 1004for the NPDSCH transmitted in subframes {5, 6, 8} may be based on thescrambling sequence of subframe 5. In addition, scrambling sequence usedby base station 1004 for the NPDSCH transmitted in subframes {10, 13}may be based on the scrambling sequence of subframe 10. Further, thescrambling sequence used by base station 1004 for the NPDSCH transmittedin subframes {14, 15, 17} may be based on subframe 14. Referring to thesecond example discussed with respect to FIG. 10, the scramblingsequence used by base station 1004 for the NPDSCH transmitted insubframes {5, 6} may be based on subframe 4, the scrambling sequenceused by base station 1004 for the NPDSCH transmitted in subframes {8,10} may be based on subframe 8, the scrambling sequence used by basestation 1004 for the NPDSCH transmitted in subframes {13, 14, 15} may bebased on subframe 12, and the scrambling sequence used by base station1004 for the NPDSCH transmitted in subframe {17} may be based onsubframe 16.

At 1610, the base station may transmit a series of repetitions of anarrowband physical downlink channel using the narrowband TDD framestructure. In one aspect, a first portion of repetitions from the seriesof repetitions may be transmitted in one or more first sets of downlinksubframes using a first scrambling sequence. In another aspect, a secondportion of repetitions from the series of repetitions may be transmittedin one or more second sets of downlink subframes using a secondscrambling sequence. In a further aspect, each of the one or more firstsets of downlink subframes may include a same number of subframes. Incertain other aspects, each of the one or more second sets of downlinksubframes may include the same number of subframes. In certain otheraspects, each of the one or more first sets of downlink subframes mayinclude a same number of subframes as each of the one or more secondsets of downlink subframes. For example, referring to FIG. 10, basestation 1004 may transmit 1009 a series of repetitions of the NPDCCHand/or NPDSCH based on either the first example or the second exampledescribed above with respect to FIG. 10.

FIG. 17 is a flowchart 1700 of a method of wireless communication. Themethod may be performed by a base station (e.g., the base station 102,180, 504, 604, 704, 804, 904, 1004, 1104, 2350, 2550, 2750, eNB 310, theapparatus 1802/1802′).

At 1702, the base station may determine a narrowband TDD frame structureof a group of narrowband TDD frame structures for narrowbandcommunications. For example, referring to FIG. 11, base station 1104 maydetermine 1101 a narrowband TDD frame structure that includes one ormore of a set of downlink subframes, a set of uplink subframes, a set ofspecial subframes, or a set of flexible subframes. For example, basestation 1104 may determine 1101 that the narrowband TDD frame structureis one of configuration 0, 1, 2, 3, 4, 5, 6, 1, or o from table 410 inFIG. 4.

At 1704, the base station may transmit a first redundancy version of anarrowband physical downlink channel and a second redundancy version ofthe narrowband physical downlink channel using the narrowband TDD framestructure. In one aspect, a number of repetitions of either redundancyversion transmitted before switching between the first redundancyversion and a second redundancy version may be based on a number ofdownlink subframes in the determined narrowband TDD frame structure anda predetermined maximum number of repetitions. In certain aspects, thenumber of downlink subframes may include a number of contiguous downlinksubframes. For example, referring to FIG. 11, base station 1104 maytransmit a first redundancy version (RV0) of the NPDCCH 1103 and/orNPDSCH 1103 and a second redundancy version (RV1) 1105 of the NPDCCH1105 and/or NPDSCH 1105 using the narrowband TDD frame structure. In oneaspect, a number of repetitions of RV0 may be transmitted in arepetition cycle before switching to RV1, and vice versa. The number ofrepetitions in a repetition cycle may be based on a number of contiguousdownlink subframes in the determined narrowband TDD frame structure anda predetermined maximum number of repetitions. As an illustrativeexample, assume configuration 1 is used for the narrowband TDD framestructure, that sixteen repetitions of the NPDCCH 1103 and/or NPDSCH1103 are configured, that two versions of repetition are configured, andthat the maximum number of repetitions in a repetition cycle is two.Thus, the sequence transmitted by base station 1104 would be {RV0RV0 RVRV0RV0 RV RV0RV0 RV RV0RV0 RV RV0RV0 RV RV0RV0 RV RV0RV0 RV RV0RV0 RV}.

FIG. 18 is a conceptual data flow diagram 1800 illustrating the dataflow between different means/components in an exemplary apparatus 1802.The apparatus may be a base station (e.g., the base station 102, 180,504, 604, 704, 804, 904, 1004, 1104, 2350, eNB 310, the apparatus 1802′,2502/2502′) in narrowband communication (e.g., NB-IoT communication oreMTC) with UE 1850 (e.g., UE 104, 350, 506, 606, 706, 806, 906, 1006,1106, 2550, apparatus 2302/2302′). The apparatus may include a receptioncomponent 1804, a scrambling sequence component 1806, a physicaldownlink channel component 1808, a subframe component 1810, and atransmission component 1812.

In certain configurations, the frame structure component 1808 may beconfigured to determine a narrowband TDD frame structure of a group ofnarrowband TDD frame structures for narrowband communications. The framestructure component 1808 may be configured to send a signal associatedwith the narrowband TDD frame structure to the transmission component1812.

In certain configurations, the subframe component 1810 may be configuredto group a plurality of subframes into a plurality of subframe groups.In one aspect, each of the plurality of subframe groups may beassociated with a particular scrambling sequence. In another aspect,each subframe group may be determined based on a downlink subframe and apredetermined number of following subframes. In a further aspect, noneof the subframe groups may have overlapping subframes. The subframecomponent 1810 may be configured to send a signal associated with theplurality of subframe groups to the transmission component 1812.

In certain other configurations, the subframe component 1810 may beconfigured to determine a first subframe group of the plurality ofsubframe groups associated with the first set of subframes and a secondsubframe group of the plurality of subframe groups associated with thesecond set of subframes. The subframe component 1810 may be configuredto send a signal associated with the first subframe group of theplurality of subframe groups associated with the first set of subframesand the second subframe group of the plurality of subframe groupsassociated with the second set of subframes to the transmissioncomponent 1812.

In certain configurations, the scrambling sequence component 1806 may beconfigured to determine a first scrambling sequence for the first set ofdownlink subframes in a first subframe group and the second scramblingsequence for a second set of downlink subframes in a second subframegroup. In one aspect, the first set of downlink subframes may include adifferent number of subframes than the second set of downlink subframes.The scrambling sequence component 1806 may be configured to send asignal associated with the first scrambling sequence and the secondscrambling sequence to the transmission component 1812.

In certain configurations, the transmission component 1812 may beconfigured to transmit a series of repetitions of a narrowband physicaldownlink channel using the narrowband TDD frame structure. In oneaspect, a first portion of repetitions from the series of repetitionsmay be transmitted in one or more first sets of downlink subframes usinga first scrambling sequence. In another aspect, a second portion ofrepetitions from the series of repetitions may be transmitted in one ormore second sets of downlink subframes using a second scramblingsequence. In a further aspect, each of the one or more first sets ofdownlink subframes may include a same number of subframes. In certainaspects, each of the one or more second sets of downlink subframes mayinclude the same number of subframes. In certain other aspects, each ofthe one or more first sets of downlink subframes may include a samenumber of subframes as each of the one or more second sets of downlinksubframes.

The apparatus may include additional components that perform each of theblocks of the algorithm in the aforementioned flowchart of FIG. 16. Assuch, each block in the aforementioned flowchart of FIG. 16 may beperformed by a component and the apparatus may include one or more ofthose components. The components may be one or more hardware componentsspecifically configured to carry out the stated processes/algorithm,implemented by a processor configured to perform the statedprocesses/algorithm, stored within a computer-readable medium forimplementation by a processor, or some combination thereof.

FIG. 19 is a diagram 1900 illustrating an example of a hardwareimplementation for an apparatus 1802′ employing a processing system1914. The processing system 1914 may be implemented with a busarchitecture, represented generally by the bus 1924. The bus 1924 mayinclude any number of interconnecting buses and bridges depending on thespecific application of the processing system 1914 and the overalldesign constraints. The bus 1924 links together various circuitsincluding one or more processors and/or hardware components, representedby the processor 1904, the components 1804, 1806, 1808, 1810, 1812 andthe computer-readable medium/memory 1906. The bus 1924 may also linkvarious other circuits such as timing sources, peripherals, voltageregulators, and power management circuits, which are well known in theart, and therefore, will not be described any further.

The processing system 1914 may be coupled to a transceiver 1910. Thetransceiver 1910 is coupled to one or more antennas 1920. Thetransceiver 1910 provides a means for communicating with various otherapparatus over a transmission medium. The transceiver 1910 receives asignal from the one or more antennas 1920, extracts information from thereceived signal, and provides the extracted information to theprocessing system 1914, specifically the reception component 1804. Inaddition, the transceiver 1910 receives information from the processingsystem 1914, specifically the transmission component 1812, and based onthe received information, generates a signal to be applied to the one ormore antennas 1920. The processing system 1914 includes a processor 1904coupled to a computer-readable medium/memory 1906. The processor 1904 isresponsible for general processing, including the execution of softwarestored on the computer-readable medium/memory 1906. The software, whenexecuted by the processor 1904, causes the processing system 1914 toperform the various functions described above for any particularapparatus. The computer-readable medium/memory 1906 may also be used forstoring data that is manipulated by the processor 1904 when executingsoftware. The processing system 1914 further includes at least one ofthe components 1804, 1806, 1808, 1810, 1812. The components may besoftware components running in the processor 1904, resident/stored inthe computer readable medium/memory 1906, one or more hardwarecomponents coupled to the processor 1904, or some combination thereof.The processing system 1914 may be a component of the eNB 310 and mayinclude the memory 376 and/or at least one of the TX processor 316, theRX processor 370, and the controller/processor 375.

In certain configurations, the apparatus 1802/1802′ for wirelesscommunication may include means for determining a narrowband TDD framestructure of a group of narrowband TDD frame structures for narrowbandcommunications. In certain other configurations, the apparatus1802/1802′ for wireless communication may include means for grouping aplurality of subframes into a plurality of subframe groups. In oneaspect, each of the plurality of subframe groups may be associated witha particular scrambling sequence. In another aspect, each subframe groupmay be determined based on a downlink subframe and a predeterminednumber of following subframes. In a further aspect, none of the subframegroups may have overlapping subframes. In certain other configurations,the apparatus 1802/1802′ for wireless communication may include meansfor determining a first subframe group of the plurality of subframegroups associated with the first set of subframes and a second subframegroup of the plurality of subframe groups associated with the second setof subframes. In certain other configurations, the apparatus 1802/1802′for wireless communication may include means for determining a firstscrambling sequence for the first set of downlink subframes in a firstsubframe group and the second scrambling sequence for a second set ofdownlink subframes in a second subframe group. In one aspect, the firstset of downlink subframes may include a different number of subframesthan the second set of downlink subframes. In certain otherconfigurations, the apparatus 1802/1802′ for wireless communication mayinclude means for transmit a series of repetitions of a narrowbandphysical downlink channel using the narrowband TDD frame structure. Inone aspect, a first portion of repetitions from the series ofrepetitions may be transmitted in one or more first sets of downlinksubframes using a first scrambling sequence. In another aspect, a secondportion of repetitions from the series of repetitions may be transmittedin one or more second sets of downlink subframes using a secondscrambling sequence. In a further aspect, each of the one or more firstsets of downlink subframes may include a same number of subframes. Incertain aspects, each of the one or more second sets of downlinksubframes may include the same number of subframes. In certain otheraspects, each of the one or more first sets of downlink subframes mayinclude a same number of subframes as each of the one or more secondsets of downlink subframes. The aforementioned means may be one or moreof the aforementioned components of the apparatus 1802 and/or theprocessing system 1914 of the apparatus 1802′ configured to perform thefunctions recited by the aforementioned means. As described above, theprocessing system 1914 may include the TX Processor 316, the RXProcessor 370, and the controller/processor 375. As such, in oneconfiguration, the aforementioned means may be the TX Processor 316, theRX Processor 370, and the controller/processor 375 configured to performthe functions recited by the aforementioned means.

FIG. 20 is a flowchart 2000 of a method of wireless communication. Themethod may be performed by a UE (e.g., the UE 104, 350, 506, 606, 706,806, 906, 1006, 1106, 1850, 2550, the apparatus 2302/2302′).

At 2002, the UE may receive information indicating a narrowband TDDframe structure of a group of narrowband TDD frame structures fornarrowband communications. For example, referring to FIG. 8A, UE 806 mayreceive information 801 indicating a narrowband TDD frame structure frombase station 804. For example, the information 801 may indicate that thenarrowband TDD frame structure is one of configuration 0, 1, 2, 3, 4, 5,6, 1, or o from table 410 in FIG. 4.

At 2004, the UE may monitor one or more downlink subframes in a firstradio frame that includes the narrowband TDD frame structure for adownlink transmission from a base station. For example, referring toFIG. 8A, UE 806 may monitor 803 one or more downlink subframes for adownlink transmission (e.g., NPDCCH and/or NPDSCH) in a first radioframe that uses the narrowband TDD frame structure.

At 2006, the UE may delay at least one uplink transmission to an uplinksubframe in a second radio frame that is subsequent to the first radioframe. For example, referring to FIG. 8A, UE 806 may delay an NPUSCHtransmission 805 to an uplink subframe located in a second radio framethat is subsequent to the first radio frame. In other words, interlacingis not enabled, and UE 806 may only monitor downlink subframes ortransmit using uplink subframes in a single radio frame, but not both.

FIG. 21 is a flowchart 2100 of a method of wireless communication. Themethod may be performed by a UE (e.g., the UE 104, 350, 506, 606, 706,806, 906, 1006, 1106, 1850, 2550, the apparatus 2302/2302′). In FIG. 21,operations with dashed lines indicate optional operations.

At 2102, the UE may receive information indicating a narrowband TDDframe structure of a group of narrowband TDD frame structures fornarrowband communications. For example, referring to FIG. 8B, UE 806 mayreceive information 801 indicating a narrowband TDD frame structure fornarrowband communications from base station 804. For example, theinformation 801 may indicate that the narrowband TDD frame structure isone of configuration 0, 1, 2, 3, 4, 5, 6, 1, or o from table 410 in FIG.4.

At 2104, the UE may receive a downlink grant associated with anarrowband physical downlink channel. For example, referring to FIG. 8B,UE 806 may receive a downlink grant 807 that allocates a first set ofsubframes for the NPDCCH 809 and/or NPDSCH 809. For example, thedownlink grant may indicate that downlink subframes p to q are allocatedfor the NPDCCH 809 and/or NPDSCH 809.

At 2106, the UE may receive the narrowband physical downlink channelassociated with the downlink grant over a plurality of subframes. In oneaspect, the plurality of subframes may include uplink subframes,downlink subframes, and special subframes. In one aspect, the narrowbandphysical downlink channel includes a NPDSCH. In a further aspect, thenarrowband physical downlink channel may be received over subframes p toq. For example, referring to FIG. 8B, UE 806 may receive the NPDCCH 809and/or NPDSCH 809 associated with the downlink grant 807 in at least onesubframe in the set of subframes p to q. In a first example associatedwith FIG. 8B, assume narrowband TDD frame structure is configuration 1,and subframes 3, 4, and 5 (e.g., p is equal to 3 and q is equal to 5)are allocated in the downlink grant 807 for the NPDCCH 809 and/or NPDSCH809.

At 2108, the UE may receive the narrowband physical downlink channelassociated with the downlink grant over a plurality of subframes byreceiving the narrowband physical downlink channel from subframe p tosubframe q. For example, referring to FIG. 8B, UE 806 may receive theNPDCCH 809 and/or NPDSCH 809 associated with the downlink grant 807 inat least one subframe in the set of subframes p to q. In a first exampleassociated with FIG. 8B, assume narrowband TDD frame structure isconfiguration 1, and subframes 3, 4, and 5 (e.g., p is equal to 3 and qis equal to 5) are allocated in the downlink grant 807 for the NPDCCH809 and/or NPDSCH 809.

At 2110, the UE may receive an uplink grant associated for a narrowbandphysical uplink channel. In one aspect, the downlink grant and theuplink grant may be received in a same search space. For example,referring to FIG. 8B, UE 806 may receive an uplink grant 811 thatallocates a second set of subframes for the NPUCCH 813 and/or NPUSCH813. For example, the second set of subframes may be located before thefirst set of subframes, located after the first set of subframes, and/orpartially overlap with the first set of subframes. In addition, UE 806may be restricted to transmit the NPUCCH 813 and/or NPUSCH 813 using asubset of subframes in the second set. In one aspect, the UE 806 may berestricted to a subset of subframes to accommodate switching fromreceiving the NPDCCH 809 and/or NPDSCH 809 to transmitting the NPUCCH813 and/or NPUSCH 813. In certain configurations, the downlink grant 807and the uplink grant 811 may be received in the same search space. Inone aspect, a NPUCCH (ACK) and a NPDSCH may not be interlaced. Referringto the first example discussed above with respect to FIG. 8B, assume theuplink grant 811 indicates that the UE 806 may transmit the NPUCCH 813and/or NPUSCH 813 in uplink subframes located in the set of subframes 1,2, 3, 4, 5, 6, 7, and 8. In addition, assume the UE 806 is restricted tosubframes that are located a number of subframes before the firstsubframe allocated for the NPDCCH 809 and/or NPDSCH 809 (e.g., subframep−a). In addition, assume UE 806 is restricted to subframes that arelocated b number of subframes after the last subframe allocated for theNPDCCH 809 and/or NPDSCH 809 (e.g., subframe q+b). Furthermore, assumethat a is equal to 1 and that b is equal to two.

At 2112, the UE may transmit the narrowband physical uplink channelassociated with the uplink grant using one or more uplink subframeslocated at least one of before the plurality of subframes or after theplurality of subframes. In one aspect, the narrowband physical uplinkchannel includes at least one of a NPUCCH or a NPUSCH. In anotheraspect, the narrowband physical uplink channel does not includes anACK/NACK associated with the NPUCCH. For example, referring to FIG. 8B,UE 806 may transmit the NPUCCH 813 and/or NPUSCH 813 using subframes 1,2, and 8 because subframe 3 is restricted (e.g., 4−1=3) for switchingand subframes 6 and 7 are also restricted (e.g., 5+2=7) for switching.

At 2114, the UE may transmit the narrowband physical uplink channelassociated with the uplink grant using one or more uplink subframeslocated at least one of before the plurality of subframes or after theplurality of subframes by transmitting the narrowband uplink physicalchannel using at least one of subframes before subframe p−a or subframesafter subframe q+b. In one aspect, a and b may be positive integers. Forexample, referring to FIG. 8B, UE 806 may transmit the NPUCCH 813 and/orNPUSCH 813 using subframes 1, 2, and 8 because subframe 3 is restricted(e.g., 4−1=3) for switching and subframes 6 and 7 are also restricted(e.g., 5+2=7) for switching.

FIG. 22 is a flowchart 2200 of a method of wireless communication. Themethod may be performed by a UE (e.g., the UE 104, 350, 506, 606, 706,806, 906, 1006, 1106, 1850, 2550, the apparatus 2302/2302′). In FIG. 22,operations with dashed lines indicate optional operations.

At 2202, the UE may receive information indicating a narrowband TDDframe structure of a group of narrowband TDD frame structures fornarrowband communications. For example, referring to FIG. 8C, UE 806 mayreceive information 801 indicating a TDD frame structure for narrowbandcommunications from base station 804. For example, the information 801may indicate that the narrowband TDD frame structure is one ofconfiguration 0, 1, 2, 3, 4, 5, 6, 1, or o from table 410 in FIG. 4.

At 2204, the UE may receive an uplink grant associated with a narrowbandphysical uplink channel. For example, referring to FIG. 8C, UE 806 mayreceive an uplink grant 815 that allocates a first set of subframes forthe NPUCCH 817 and/or NPUSCH 817. For example, the uplink grant 815 mayindicate that downlink subframes p to q are allocated for the NPUCCH 817and/or NPUSCH 817.

At 2206, the UE may transmit the narrowband physical uplink channelassociated with the uplink grant over a plurality of subframes. In oneaspect, the plurality of subframes may include uplink subframes,downlink subframes, and special subframes. For example, referring toFIG. 8C, UE 806 may transmit the NPUCCH 817 and/or NPUSCH 817 associatedwith the uplink grant 815 in at least one subframe in the set ofsubframes p to q. As an illustrative example, assume narrowband TDDframe structure is configuration 1, and subframes 6 and 7 (e.g., p isequal to 6 and q is equal to 7) are allocated in the uplink grant 815for the NPUCCH 817 and/or NPUSCH 817. In other words, the first set ofsubframes may include a special subframe 6 and uplink subframe 7.

At 2208, the UE may transmit the narrowband physical uplink channelassociated with the uplink grant over a plurality of subframes bytransmitting the narrowband physical uplink channel from subframe p tosubframe q. For example, referring to FIG. 8C, may transmit the NPUCCH817 and/or NPUSCH 817 associated with the uplink grant 815 in at leastone subframe in the set of subframes p to q.

At 2210, the UE may receive a downlink grant for a narrowband physicaldownlink channel. For example, referring to FIG. 8C, UE 806 may receivedownlink grant 819 that allocates a second set of subframes for theNPDCCH 821 and/or NPDSCH 821. For example, the second set of subframesmay be located before the first set of subframes, located after thefirst set of subframes, and/or partially overlap with the first set ofsubframes. In addition, UE 806 may be restricted to monitor a subset ofsubframes in the second set for the NPDCCH 821 and/or NPDSCH 821. In oneaspect, the UE 806 may be restricted to monitor only a set of theallocated downlink subframes to accommodate switching from transmittingthe NPUCCH 817 and/or NPUSCH 817 to monitoring for the NPDCCH 821 and/orNPDSCH 821.

At 2212, the UE may receive the narrowband physical downlink channelassociated with the downlink grant in one or more downlink subframeslocated at least one of before the plurality of subframes or after theplurality of subframes. For example, referring to FIG. 8C, UE 806 mayreceive the NPDCCH 821 and/or NPDSCH 821 in the second set of subframes.For example, the second set of subframes may be located before the firstset of subframes, located after the first set of subframes, and/orpartially overlap with the first set of subframes. In addition, UE 806may be restricted to monitor a subset of subframes in the second set forthe NPDCCH 821 and/or NPDSCH 821. In one aspect, the UE 806 may berestricted to monitor only a set of the allocated downlink subframes toaccommodate switching from transmitting the NPUCCH 817 and/or NPUSCH 817to monitoring for the NPDCCH 821 and/or

NPDSCH 821 that may be received in the second set of subframes.Referring to the example discussed above with respect to FIG. 8C, assumethe downlink grant 819 indicates that the UE 806 that downlink subframeslocated between subframes 4, 5, 6, 7, 8, and 9 are allocated for theNPDCCH 821 and/or NPDSCH 821. In addition, assume the UE 806 isrestricted to subframes that are located c number of subframes beforethe first subframe allocated for the NPUCCH 817 and/or NPUSCH 817 (e.g.,subframe p−c). In addition, assume UE 806 is restricted to subframesthat are located d number of subframes after the last subframe allocatedfor the NPUCCH 817 and/or NPUSCH 817 (e.g., subframe q+d). Furthermore,assume that c is equal to 1 and that d is equal to one. Hence, UE 806may monitor downlink subframes 4 and 9 and not subframe 5 becausesubframe 5 is restricted (e.g., 6−1=5) for switching. There are nodownlink subframes located after subframe 7, and thus no downlinksubframes after subframe 7 are restricted for switching.

At 2214, the UE may receive the narrowband physical downlink channelassociated with the downlink grant in one or more downlink subframeslocated at least one of before the plurality of subframes or after theplurality of subframes by receiving the narrowband downlink physicalchannel using at least one of subframes before subframe p−c or subframesafter subframe q+d. In one aspect, c and d may be positive integers. Forexample, referring to FIG. 8C, UE 806 may receive the NPDCCH 821 and/orNPDSCH 821 in the second set of subframes. For example, the second setof subframes may be located before the first set of subframes, locatedafter the first set of subframes, and/or partially overlap with thefirst set of subframes. In addition, UE 806 may be restricted to monitora subset of subframes in the second set for the NPDCCH 821 and/or NPDSCH821. In one aspect, the UE 806 may be restricted to monitor only a setof the allocated downlink subframes to accommodate switching fromtransmitting the NPUCCH 817 and/or NPUSCH 817 to monitoring for theNPDCCH 821 and/or NPDSCH 821 that may be received in the second set ofsubframes. Referring to the example discussed above with respect to FIG.8C, assume the downlink grant 819 indicates that the UE 806 thatdownlink subframes located between subframes 4, 5, 6, 7, 8, and 9 areallocated for the NPDCCH 821 and/or NPDSCH 821. In addition, assume theUE 806 is restricted to subframes that are located c number of subframesbefore the first subframe allocated for the NPUCCH 817 and/or NPUSCH 817(e.g., subframe p−c). In addition, assume UE 806 is restricted tosubframes that are located d number of subframes after the last subframeallocated for the NPUCCH 817 and/or NPUSCH 817 (e.g., subframe q+d).

Furthermore, assume that c is equal to 1 and that d is equal to one.Hence, UE 806 may monitor downlink subframes 4 and 9 and not subframe 5because subframe 5 is restricted (e.g., 6−1=5) for switching. There areno downlink subframes located after subframe 7, and thus no downlinksubframes after subframe 7 are restricted for switching.

FIG. 23 is a conceptual data flow diagram 2300 illustrating the dataflow between different means/components in an exemplary apparatus 2302.The apparatus may be a UE (e.g., the UE 104, 350, 506, 606, 706, 806,906, 1006, 1106, 2550, the apparatus 2302′) in narrowband communication(e.g., NB-IoT communication or eMTC) with base station 2350 (e.g., basestation 102, 180, 504, 604, 704, 804, 904, 1004, 1104, the apparatus1802/1802′, 2502/2502′, eNB 310). The apparatus may include a receptioncomponent 2304, a monitoring component 2306, a transmission component2308, and a delaying component 2310.

In certain configurations, the reception component 2304 may beconfigured to receive information indicating a narrowband TDD framestructure of a group of narrowband TDD frame structures for narrowbandcommunications. The reception component 2304 may be configured to send asignal associated with the information indicating a narrowband TDD framestructure of a group of narrowband TDD frame structures for narrowbandcommunications to one or more of the monitoring component 2306, thetransmission component 2308, and/or the delaying component 2310.

In certain configurations, the monitoring component 2306 may beconfigured to monitor one or more downlink subframes in a first radioframe that includes the narrowband TDD frame structure for a downlinktransmission from the base station 2350. In certain aspects, themonitoring component 2306 may be configured to monitor one or moredownlink subframes in the first radio frame by communicating with thereception component 2304 and/or the transmission component 2308.

In certain configurations, the delaying component 2310 may be configuredto delay at least one uplink transmission to an uplink subframe in asecond radio frame that is subsequent to the first radio frame. Thedelaying component 2310 may be configured to send a signal to thetransmission component 2308 indicating that at least one uplinktransmission is delayed to an uplink subframe in a second radio framethat is subsequent to the first radio frame.

The apparatus may include additional components that perform each of theblocks of the algorithm in the aforementioned flowchart of FIG. 20. Assuch, each block in the aforementioned flowchart of FIG. 20 may beperformed by a component and the apparatus may include one or more ofthose components. The components may be one or more hardware componentsspecifically configured to carry out the stated processes/algorithm,implemented by a processor configured to perform the statedprocesses/algorithm, stored within a computer-readable medium forimplementation by a processor, or some combination thereof.

FIG. 24 is a diagram 2400 illustrating an example of a hardwareimplementation for an apparatus 2302′ employing a processing system2414. The processing system 2414 may be implemented with a busarchitecture, represented generally by the bus 2424. The bus 2424 mayinclude any number of interconnecting buses and bridges depending on thespecific application of the processing system 2414 and the overalldesign constraints. The bus 2424 links together various circuitsincluding one or more processors and/or hardware components, representedby the processor 2404, the components 2304, 2306, 2308, 2310 and thecomputer-readable medium/memory 2406. The bus 2424 may also link variousother circuits such as timing sources, peripherals, voltage regulators,and power management circuits, which are well known in the art, andtherefore, will not be described any further.

The processing system 2414 may be coupled to a transceiver 2410. Thetransceiver 2410 is coupled to one or more antennas 2420. Thetransceiver 2410 provides a means for communicating with various otherapparatus over a transmission medium. The transceiver 2410 receives asignal from the one or more antennas 2420, extracts information from thereceived signal, and provides the extracted information to theprocessing system 2414, specifically the reception component 2304. Inaddition, the transceiver 2410 receives information from the processingsystem 2414, specifically the transmission component 2308, and based onthe received information, generates a signal to be applied to the one ormore antennas 2420. The processing system 2414 includes a processor 2404coupled to a computer-readable medium/memory 2406. The processor 2404 isresponsible for general processing, including the execution of softwarestored on the computer-readable medium/memory 2406. The software, whenexecuted by the processor 2404, causes the processing system 2414 toperform the various functions described above for any particularapparatus. The computer-readable medium/memory 2406 may also be used forstoring data that is manipulated by the processor 2404 when executingsoftware. The processing system 2414 further includes at least one ofthe components 2304, 2306, 2308, 2310. The components may be softwarecomponents running in the processor 2404, resident/stored in thecomputer readable medium/memory 2406, one or more hardware componentscoupled to the processor 2404, or some combination thereof. Theprocessing system 2414 may be a component of the UE 350 and may includethe memory 360 and/or at least one of the TX processor 368, the RXprocessor 356, and the controller/processor 359.

In certain configurations, the apparatus 2302/2302′ for wirelesscommunication may include means for receiving information indicating anarrowband TDD frame structure of a group of narrowband TDD framestructures for narrowband communications. In certain otherconfigurations, the apparatus 2302/2302′ for wireless communication mayinclude means for monitoring one or more downlink subframes in a firstradio frame that includes the narrowband TDD frame structure for adownlink transmission from a base station. In certain otherconfigurations, the apparatus 2302/2302′ for wireless communication mayinclude means for delaying at least one uplink transmission to an uplinksubframe in a second radio frame that is subsequent to the first radioframe. The aforementioned means may be one or more of the aforementionedcomponents of the apparatus 2302 and/or the processing system 2414 ofthe apparatus 2302′ configured to perform the functions recited by theaforementioned means. As described above, the processing system 2414 mayinclude the TX Processor 368, the RX Processor 356, and thecontroller/processor 359. As such, in one configuration, theaforementioned means may be the TX Processor 368, the RX Processor 356,and the controller/processor 359 configured to perform the functionsrecited by the aforementioned means.

FIG. 25 is a conceptual data flow diagram 2500 illustrating the dataflow between different means/components in an exemplary apparatus 2502.The apparatus may be a base station (e.g., the base station 102, 180,504, 604, 704, 804, 904, 1004, 1104, 2350, eNB 310, the apparatus1802/1802′, 2502′) in narrowband communication (e.g., NB-IoTcommunication or eMTC) with UE 2550 (e.g., UE 104, 350, 506, 606, 706,806, 906, 1006, 1106, 1850, apparatus 2302/2302′). The apparatus mayinclude a reception component 2504, a physical downlink channelcomponent 2506, and a transmission component 2508.

In certain configurations, the frame structure component 2506 may beconfigured to determine a narrowband TDD frame structure of a group ofnarrowband TDD frame structures for narrowband communications. The framestructure component 2506 may be configured to send a signal associatedwith the narrowband TDD frame structure to the transmission component2508.

In certain other configurations, the frame structure component 2506 maybe configured to determine a first redundancy version of a narrowbandphysical downlink channel and a second redundancy version of thenarrowband physical downlink channel using the narrowband TDD framestructure. In one aspect, a number of repetitions of either redundancyversion transmitted before switching between the first redundancyversion and a second redundancy version may be based on a number ofdownlink subframes in the determined narrowband TDD frame structure anda predetermined maximum number of repetitions. In certain aspects, thenumber of downlink subframes may include a number of contiguous downlinksubframes. The frame structure component 2506 may be configured to senda signal associated with the first redundancy version of the narrowbandphysical downlink channel and the second redundancy version of thenarrowband physical downlink channel using the narrowband TDD framestructure to the transmission component 2508.

In certain configurations, the transmission component 2508 may beconfigured to transmit a first redundancy version of a narrowbandphysical downlink channel and a second redundancy version of thenarrowband physical downlink channel using the narrowband TDD framestructure. In one aspect, a number of repetitions of either redundancyversion transmitted before switching between the first redundancyversion and a second redundancy version may be based on a number ofdownlink subframes in the determined narrowband TDD frame structure anda predetermined maximum number of repetitions. In certain aspects, thenumber of downlink subframes may include a number of contiguous downlinksubframes.

The apparatus may include additional components that perform each of theblocks of the algorithm in the aforementioned flowchart of FIG. 17. Assuch, each block in the aforementioned flowchart of FIG. 17 may beperformed by a component and the apparatus may include one or more ofthose components. The components may be one or more hardware componentsspecifically configured to carry out the stated processes/algorithm,implemented by a processor configured to perform the statedprocesses/algorithm, stored within a computer-readable medium forimplementation by a processor, or some combination thereof.

FIG. 26 is a diagram 2600 illustrating an example of a hardwareimplementation for an apparatus 2502′ employing a processing system2614. The processing system 2614 may be implemented with a busarchitecture, represented generally by the bus 2624. The bus 2624 mayinclude any number of interconnecting buses and bridges depending on thespecific application of the processing system 2614 and the overalldesign constraints. The bus 2624 links together various circuitsincluding one or more processors and/or hardware components, representedby the processor 2604, the components 2504, 2506, 2508, and thecomputer-readable medium/memory 2606. The bus 2624 may also link variousother circuits such as timing sources, peripherals, voltage regulators,and power management circuits, which are well known in the art, andtherefore, will not be described any further.

The processing system 2614 may be coupled to a transceiver 2610. Thetransceiver 2610 is coupled to one or more antennas 2620. Thetransceiver 2610 provides a means for communicating with various otherapparatus over a transmission medium. The transceiver 2610 receives asignal from the one or more antennas 2620, extracts information from thereceived signal, and provides the extracted information to theprocessing system 2614, specifically the reception component 2504. Inaddition, the transceiver 2610 receives information from the processingsystem 2614, specifically the transmission component 2508, and based onthe received information, generates a signal to be applied to the one ormore antennas 2620. The processing system 2614 includes a processor 2604coupled to a computer-readable medium/memory 2606. The processor 2604 isresponsible for general processing, including the execution of softwarestored on the computer-readable medium/memory 2606. The software, whenexecuted by the processor 2604, causes the processing system 2614 toperform the various functions described supra for any particularapparatus. The computer-readable medium/memory 2606 may also be used forstoring data that is manipulated by the processor 2604 when executingsoftware. The processing system 2614 further includes at least one ofthe components 2504, 2506, 2508. The components may be softwarecomponents running in the processor 2604, resident/stored in thecomputer readable medium/memory 2606, one or more hardware componentscoupled to the processor 2604, or some combination thereof. Theprocessing system 2614 may be a component of the base station 310 andmay include the memory 376 and/or at least one of the TX processor 316,the RX processor 370, and the controller/processor 375.

In certain configurations, the apparatus 2502/2502′ for wirelesscommunication may include means for determining a narrowband TDD framestructure of a group of narrowband TDD frame structures for narrowbandcommunications. In certain other configurations, the apparatus2502/2502′ for wireless communication may include means for transmittinga first redundancy version of a narrowband physical downlink channel anda second redundancy version of the narrowband physical downlink channelusing the narrowband TDD frame structure. In one aspect, a number ofrepetitions of either redundancy version transmitted before switchingbetween the first redundancy version and a second redundancy version maybe based on a number of downlink subframes in the determined narrowbandTDD frame structure and a predetermined maximum number of repetitions.In certain aspects, the number of downlink subframes may include anumber of contiguous downlink subframes. The aforementioned means may beone or more of the aforementioned components of the apparatus 2502and/or the processing system 2614 of the apparatus 2502′ configured toperform the functions recited by the aforementioned means. As describedsupra, the processing system 2614 may include the TX Processor 316, theRX Processor 370, and the controller/processor 375. As such, in oneconfiguration, the aforementioned means may be the TX Processor 316, theRX Processor 370, and the controller/processor 375 configured to performthe functions recited by the aforementioned means.

It is understood that the specific order or hierarchy of blocks in theprocesses/flowcharts disclosed is an illustration of exemplaryapproaches. Based upon design preferences, it is understood that thespecific order or hierarchy of blocks in the processes/flowcharts may berearranged. Further, some blocks may be combined or omitted. Theaccompanying method claims present elements of the various blocks in asample order, and are not meant to be limited to the specific order orhierarchy presented.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but is to be accorded the full scope consistentwith the language claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” The word “exemplary” is used hereinto mean “serving as an example, instance, or illustration.” Any aspectdescribed herein as “exemplary” is not necessarily to be construed aspreferred or advantageous over other aspects. Unless specifically statedotherwise, the term “some” refers to one or more. Combinations such as“at least one of A, B, or C,” “one or more of A, B, or C,” “at least oneof A, B, and C,” “one or more of A, B, and C,” and “A, B, C, or anycombination thereof” include any combination of A, B, and/or C, and mayinclude multiples of A, multiples of B, or multiples of C. Specifically,combinations such as “at least one of A, B, or C,” “one or more of A, B,or C,” “at least one of A, B, and C,” “one or more of A, B, and C,” and“A, B, C, or any combination thereof” may be A only, B only, C only, Aand B, A and C, B and C, or A and B and C, where any such combinationsmay contain one or more member or members of A, B, or C. All structuraland functional equivalents to the elements of the various aspectsdescribed throughout this disclosure that are known or later come to beknown to those of ordinary skill in the art are expressly incorporatedherein by reference and are intended to be encompassed by the claims.Moreover, nothing disclosed herein is intended to be dedicated to thepublic regardless of whether such disclosure is explicitly recited inthe claims. The words “module,” “mechanism,” “element,” “device,” andthe like may not be a substitute for the word “means.” As such, no claimelement is to be construed as a means plus function unless the elementis expressly recited using the phrase “means for.”

What is claimed is:
 1. A method of wireless communications for a userequipment, comprising: determining a time-division duplex (TDD) framestructure of a group of TDD frame structures being used by a radioaccess network for narrowband communications; receiving, from a basestation, a series of repetitions of a narrowband physical downlinkchannel using the narrowband TDD frame structure, wherein a firstportion of repetitions from the series of repetitions comprises a firstsubframe group and a second portion of repetitions from the series ofrepetitions comprises a second subframe group; wherein the firstsubframe group comprises a first set of downlink subframes scrambledusing a first scrambling sequence, the first set of downlink subframesincluding a first downlink subframe and a predetermined first number offollowing subframes; and wherein the second subframe group comprises asecond set of downlink subframes scrambled using a second scramblingsequence, the second set of downlink subframes including a seconddownlink subframe and a predetermined second number of followingsubframes, and the first subframe group and the second subframe group donot overlap.
 2. The method of claim 1, wherein the first set of downlinksubframes includes a same number of subframes as the second set ofdownlink subframes.
 3. The method of claim 1, wherein the series ofrepetitions comprises a plurality of subframe groups, each of theplurality of subframe groups being associated with a particularscrambling sequence, and each subframe group being determined based on adownlink subframe and a predetermined number of following subframes, andwherein none of the subframe groups have overlapping subframes.
 4. Themethod of claim 3, wherein each of the plurality of subframe groupscomprises four or less subframes.
 5. The method of claim 3, wherein thefirst set of downlink subframes includes a different number of subframesthan the second set of downlink subframes.
 6. The method of claim 1,wherein the first subframe group and the second subframe group eachcomprise four or less subframes.
 7. An apparatus for wirelesscommunications for a user equipment, comprising: means for determining atime-division duplex (TDD) frame structure of a group of TDD framestructures being used by a radio access network for narrowbandcommunications; means for receiving, from a base station, a series ofrepetitions of a narrowband physical downlink channel using thenarrowband TDD frame structure, wherein a first portion of repetitionsfrom the series of repetitions comprises a first subframe group and asecond portion of repetitions from the series of repetitions comprises asecond subframe group; wherein the first subframe group comprises afirst set of downlink subframes scrambled using a first scramblingsequence, the first set of downlink subframes including a first downlinksubframe and a predetermined first number of following subframes; andwherein the second subframe group comprises a second set of downlinksubframes scrambled using a second scrambling sequence, the second setof downlink subframes including a second downlink subframe and apredetermined second number of following subframes, and the firstsubframe group and the second subframe group do not overlap.
 8. Theapparatus of claim 7, wherein the first set of downlink subframesincludes a same number of subframes as the second set of downlinksubframes.
 9. The apparatus of claim 7, wherein the series ofrepetitions comprises a plurality of subframe groups, each of theplurality of subframe groups being associated with a particularscrambling sequence, and each subframe group being determined based on adownlink subframe and a predetermined number of following subframes, andwherein none of the subframe groups have overlapping subframes.
 10. Theapparatus of claim 9, wherein each of the plurality of subframe groupscomprise four or less subframes.
 11. The apparatus of claim 9, whereinthe first set of downlink subframes includes a different number ofsubframes than the second set of downlink subframes.
 12. The apparatusof claim 7, wherein the first subframe group and the second subframegroup each comprise four or less subframes.
 13. An apparatus forwireless communications for a user equipment, comprising: a memory; andat least one processor coupled to the memory and configured to:determine a time-division duplex (TDD) frame structure of a group of TDDframe structures being used by a radio access network for narrowbandcommunications; receive, from a base station, a series of repetitions ofa narrowband physical downlink channel using the narrowband TDD framestructure, wherein a first portion of repetitions from the series ofrepetitions comprises a first subframe group and a second portion ofrepetitions from the series of repetitions comprises a second subframegroup; wherein the first subframe, group comprises a first set ofdownlink subframes scrambled using a first scrambling sequence, thefirst set of downlink subframes including a first downlink subframe anda predetermined first number of following subframes; and wherein thesecond subframe group comprises a second set of downlink subframesscrambled using a second scrambling sequence, the second set of downlinksubframes including a second downlink subframe and a predeterminedsecond number of following subframes, and the first subframe group andthe second subframe group do not overlap.
 14. The apparatus of claim 13,wherein the first set of downlink subframes includes a same number ofsubframes as the second set of downlink subframes.
 15. The apparatus ofclaim 13, wherein the series of repetitions comprises a plurality ofsubframe groups, each of the plurality of subframe groups beingassociated with a particular scrambling sequence, and each subframegroup being determined based on a downlink subframe and a predeterminednumber of following subframes, and wherein none of the subframe groupshave overlapping subframes.
 16. The apparatus of claim 15, wherein eachof the plurality of subframe groups comprise four or less subframes. 17.The apparatus of claim 15, wherein the first set of downlink subframesincludes a different number of subframes than the second set of downlinksubframes.
 18. The apparatus of claim 13, wherein the first subframegroup and the second subframe group each comprise four or lesssubframes.
 19. A non-transitory computer-readable medium storingcomputer executable code for a user equipment, the code when executed bya processor cause the processor to: determine a time-division duplex(TDD) frame structure of a group of TDD frame structures being used by aradio access network for narrowband communications; receive, from a basestation, a series of repetitions of a narrowband physical downlinkchannel using the narrowband TDD frame structure, wherein a firstportion of repetitions from the series of repetitions comprises a firstsubframe group and a second portion of repetitions from the series ofrepetitions comprises a second subframe group; wherein the firstsubframe group comprises a first set of downlink subframes scrambledusing a first scrambling sequence, the first set of downlink subframesincluding a first downlink subframe and a predetermined first number offollowing, subframes; and wherein the second subframe group comprises asecond set of downlink subframes scrambled using a second scramblingsequence, the second set of downlink subframes including a seconddownlink subframe and a predetermined second number of followingsubframes, and the first subframe group and the second subframe group donot overlap.
 20. The non-transitory computer-readable medium of claim19, wherein the first set of downlink subframes includes a same numberof subframes as the second set of downlink subframes.
 21. Thenon-transitory computer-readable medium of claim 19, wherein the seriesof repetitions comprises a plurality of subframe groups, each of theplurality of subframe groups being associated with a particularscrambling sequence, and each subframe group being determined based on adownlink subframe and a predetermined number of following subframes, andwherein none of the subframe groups have overlapping subframes.
 22. Thenon-transitory computer-readable medium of claim 21, wherein each of theplurality of subframe groups comprise four or less subframes.
 23. Thenon-transitory computer-readable medium of claim 21, wherein the firstset of downlink subframes includes a different number of subframes thanthe second set of downlink subframes.
 24. The non-transitorycomputer-readable medium of claim 19, wherein the first subframe groupand the second subframe group each comprise four or less subframes.